Spin lever: Why is «spin cocking» lever actions commonly acceptable? : Firearms

Brakes/Levers/Pads — Spin Bike Shop

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TRP
6-Bolt Rotor Spacer

$3.99

Can be used to provide extra clearance between brake caliper and spokes.
Spacer should be placed between rotor and hub.

Syntace
Disc Brake Rotor Shims

$9.50

— Stainless steel shim helps center the rotor perfectly within the disc brake caliper
— Great for swapping wheelsets without the threat of brake drag

Shimano
105 5800 Road Brake R55C4 Shoe Set

$21.99

— Aluminum pad holder with R55C4 pads

Shimano
Altus BR-CT91 Cantilever Brake with Link Wire

$13.99 — $16.99

Shimano Altus BR-CT91 cantilever brakes offer confident and reliable braking at a convenient price point.
— Brake Lever Actuation: Short Pull
— Brake Mount Type: Canti Studs
— Material: Aluminum
— Pad Attachment Style: Threaded Post
— Weight: 204g

Shimano
Deore XT M8000 Metal Disc Brake Pad (G04S) and Spring

$22. 00

Shimano G04S metal disc brake pads.
— Fits XTR BR-M9000, BR-M9020, BR-M985, XT BR-M8000, BR-M785, SLX BR-M666, Alfine BR-S700 and BR-R785, BR-RS785 road disc calipers
— Sintered Metal pad with consistent, high stopping power in wet or dry conditions and excellent durability
— Ventilated steel backing plate for improved heat dispersion
— Backing Plate Material: Steel
— Compound: Metal

Shimano
Dura Ace Di2 ST-R9270/BR-R9270 Disc Brake Caliper/Lever Set

$768.99

All-new lever ergonomics on the DURA-ACE ST-R9270 dual control levers bring new levels comfort and control to road cycling. With our fastest wireless shifting available and even more precise brake modulation, DURA-ACE redefines performance.
Now featuring SERVO WAVE ACTION brake technology, the new DURA-ACE ST-R9270 brake lever delivers modulation and control like never before. Wireless shifting keeps your bike looking clean while offering our fastest, most precise gear changes available. All of this resides in a DUAL CONTROL LEVER to employs the most advanced materials to offer light weight and refined ergonomics that provide comfort and control for the most demanding conditions.
Clean Cockpit: Wireless connection enhances the aesthetic of your bike while keeping shifting lightning fast
1.5 to 2 years of battery life with easy-to-change CR1632 shifter batteries
Unparalleled ergonomics engineering refined with pros’ feedback
— Raised hood peak improves ergonomics, while a longer hood body increases hand support
— Compatible with satellite shifters
SERVO WAVE technology optimizes brake control
— Lighter, smoother lever action
— Enhanced modulation thanks to an expanded braking control area
Advanced Materials
— Carbon fiber brake lever and titanium hardware
Compatible with wired connection (for e-bike application)
Make DURA-ACE yours with custom button function and adjustable ergonomics
— Easily change button function with the E-TUBE app
— Find your optimum lever position with simple reach adjust

Shimano
J-Type Metallic Pads

$35.00

— Pair of J-Type disc brake pads with fins, for 1 caliper
— Available with resin or metallic compound
— Fits 2-piston SLX and XT calipers from 10 to 12 speed groups and 10 or 11 speed XTR brakes
— Ice Technologies fins & aluminum backplate cools down the brakes in use, which improves braking consistency and power and reduces brake fade during long, technical dowhnill stretches
— Longer lasting than G-type pads
— Interchangeable with F-Type and G-Type pads
— Includes spring and pin

Shimano
L-Type Metallic Pads

$36. 00

— Pair of L-Type brake pads with fins, for one caliper
— Ice Technologies fins & aluminum backplate cools down the brakes in use, which improves braking consistency and power and reduces brake fade, especially in long descents
— Choice of compound: Resin, for improved modulation & lower noise, or Metallic, for improved durability & higher braking power in muddy conditions
— Longer lasting than K-Type pads
— Interchangeable with K-type finless pads
— Fits all Shimano flat mount gravel & road disc calipers, including Dura Ace BR-R9170, Ultegra BR-R8070, 105 BR-R7070, GRX BR-RX810 and BR-RX400
— NOT compatible with XTR BR-M9100

Shimano
M70R2 Severe Condition V-Brake Pads Pair

Shimano Replacement pads for Mountain brake shoes
— Color: Black
— Intended Brake Type: Linear Pull
— Pad Attachment Style: Threaded Post
— Pad Type: Replacement Insert — Cartridge
— Rim Compatibility: Standard
— Shimano Cartridge-type mountain brake pads fit models: XTR BR-M970, BR-M960, BR-M951, BR-M950 XT BR-T780, BR-M770, BR-M760, BR-M750, BR-M739, BR-M737 LX BR-T670, BR-M580, BR-M570 Deore BR-M530, BR-M510 Alivio BR-M430, BR-MC18 Acera BR-M422, BR-M421, BR-M420, BR-M330, BR-T300 DXR BR-MX70 MX BR-M600
— M70R2: Severe condition brake pad, high performance in dry or wet conditions

Shimano
R55C4 Road Brake Pads

$10. 00 — $15.00

Shimano Replacement pads for Road brake shoes
— Color: Black
— Intended Brake Type: Caliper
— Pad Attachment Style: Bolt-In (Caliper)
— Pad Type: Replacement Insert — Cartridge
— Rim Compatibility: Standard
— Shimano Cartridge-type road brake pads fit models: Dura-Ace BR-9000, BR-9010, BR-7900, BR-7800, BR7700 Ultegra BR-6800, BR-6700, BR-6600, BR-6500 105 BR-5800, BR-5700, BR-5500 Non-Series BR-R600, BR-R561, BR-R560, BR-CX70s

Shimano
SLX BR-M7100 Disc Brake with Lever

$136.99

With a focus on reduced weight and cross-country tuned stopping power, Shimano SLX M7100 brakes provide intuitive modulation so that you can explore your limits with confidence. The BL-M7100 levers feature an optimized lever axle position, an additional handlebar contact point for greater stiffness, and refined ergonomics for rider comfort. At the caliper end, the BR-M7100 2-piston caliper provides lightweight braking performance and is combined with quicker piston retraction.
— 10% stiffer than previous generation M7000 even under high-temp conditions
— Quicker brake engagement with shorter free stroke
— Tool-free lever reach adjustment
— I-SPEC EV Clamp Band enables optional integrated shifter setup

Shimano
SLX BR-M7120 Disc Brake with Lever

$186.99

With a focus on reduced weight and cross-country tuned stopping power, Shimano SLX M7120 brakes provide intuitive modulation so that you can explore your limits with confidence. The BL-M7100 levers feature an optimized lever axle position, an additional handlebar contact point for greater stiffness, and refined ergonomics for rider comfort. At the caliper end, the BR-M7120 4-piston caliper is optimized for the toughest enduro trails.
— 10% stiffer than previous generation M7000, even under high-temp conditions
— Quicker brake engagement with shorter free stroke
— Tool-free lever reach adjustment
— I-SPEC EV Clamp Band enables optional integrated shifter setup
— Includes finned metal pads

Shimano
Ultegra RT800 Centerlock IceTech Disc Brake Rotor

$58. 99

Shimano Ultegra RT800 centerlock disc rotors.
— Aluminum spider
— Includes standard type rotor lockring
— Freeza technology, 3-layer structure with aluminum core and stainless steel outer layers and additional aluminum cooling fins reduces rotor surface temperature approximately 150 degrees Celsius compared to all-steel rotors
— Requires external-type rotor lockring when installing onto 15/20mm axle hub
— Hub/Disc Compatibility: Center-Lock Disc
— Pad Compatibility: All Pad Compounds
— Rotor Type: Two Piece

Shimano
XTR RT-MT900 Disc Brake Rotor

$81.99 — $87.99

The pinnacle in mountain bike braking, SHIMANO XTR RT-MT900 disc brake rotors deliver superb stopping power for the most aggressive riding. The ICE TECHNOLOGIES FREEZA rotors dissipate heat to maintain braking performance on long downhill stretches. SHIMANO’s CENTER LOCK mounting system makes installing and removing rotors quick and easy thanks to the spine mount and lock ring design.
High-performance and consistent brake performance
— Stable and versatile brake performance in the most demanding conditions
New ICE TECHNOLOGIES FREEZA construction for boosting heat dissipation
— Surface temperature cooled by -20°C (vs RT99, 203 mm)
Rotor size
— 160 mm, 180 mm, 203 mm

SRAM
CenterLine Rotor with Rounded Edge

$44. 00 — $55.00

Stainless steel rotor designed for smooth and quiet braking with any disc brake caliper.

SRAM
Centerline CenterLock Rotor

$45.00 — $55.00

The CenterLine design provides a smooth, consistent, and quiet running braking surface. Rounded edges make for easier wheel installs and are UCI-compliant.
— Compatible with both road and mountain bike brakes
— Rounded edges are UCI-compliant and allow for easier wheel installs
— Hub interface: CenterLock
— Rotor Type: Centerline

SRAM
Level Disc Brake

$70.00

The SRAM Level brake levels the playing field with power and reliability stuffed into a lightweight package. This is no-nonsense performer, but don’t let its understated disposition fool you—Level gives you the art of braking in minimalist form.

SRAM
Level Ultimate Brake/Lever

$285.00

Level Ultimate is the master of two forces—power and weight—in one sleek, durable design. In this build, we took every gram to task. Carbon-fiber lever blades for crisp, clean pulls. A new two-piece, two-piston caliper for superior heat management and smooth piston actuation. With Ultimate, total control is at your fingertips.
— Modern XC power for today’s most demanding races
— Pivot bearings offer crisp lever feel and a fatigue-free ride
— Engineered for easy installation and maintenance

SRAM
Pad Insert Carbon Rim (SRAM/Shimano)

$45.00

SRAM’s Pad Inserts for carbon wheels are the perfect upgrade for your brakes to deliver excellent stopping power and speed modulation. The secret is SwissStop’s proprietary yellow compound that resists heat buildup for a consistent grip without being «grabby.» They have deep grooves to whisk away water so they’re perfect for road and cyclocross alike.

SRAM
Road Disc Organic Brake Pads

$27.00 — $30.00

SRAM road disc brake pads are designed for use with SRAM road hydraulic disc brakes (HRD).
— For use with Level Ultimate & Level TLM Brakes
— Pad Material: Organic
— Type: Road/CX
— Includes guide pin, clip, & pad spreader

SRAM
Road Disc Sintered Brake Pads

$25. 00

Original equipment pads for no-compromise disc brake performance.
— Pad Shape Number: 37

SRAM
Trail/Guide Disc Brake Pads

$27.00 — $33.00

SRAM’s Disc Brake Pads are reliable and rugged. These pads are compatible with Avid Trail and SRAM Guide and G2 disc brakes.

Odyssey
1999 Caliper Brake and Lever Set

$18.30

The 1999 brake kit is a lightweight alloy brake kit perfect for those rebuilding that old BMX bike they found at a garage sale. This kit includes a brake cable, universal brake caliper, front and rear pivot bolts, alloy brake lever and all necessary hardware.
Features
— Side pull style brake
— Works with front or Rear
— Includes brake, lever, and cable
— 13.8 oz

Odyssey
Slim-By-Four Brake Pads

$8.99

The Slim by Four is a BMX-specific brake pad with a symmetrical shape designed for both forwards and backwards braking. A custom inner frame helps to stiffen the pad and prevents excessive braking power from being lost to flex.
SPECS
— Clear and Gum colored “Soft” compound pads provide extra grip on powder coated rims.
— Black “Normal” compound Slim-By-Four pads are the most popular pad choice for most riders.

Magura
7.P Disc Brake Pads

$30.93

— For long tours these pads offer safety together with excellent performance in all situations.
— For MT disc brake 2 piston
— 2 single brake pads, 2 pad retaining bolts

Magura
8.S Disc Brake Pads

$25.00

8 Series Disc Brake Pads
— Disconnected two piece back plate
— The Sport Compound offers powerful braking, high durability, and short bed-in time, making it the perfect brake pad for use with e-bikes
— Set of four disc brake pads and two pad retaining bolts for one caliper

Magura
Rim Brake Pads

$38.83

— Black: all-around performance compound
— Salmon (Kool Stop): high grip compound for race/trials use

Kool-Stop
Campi 2000 Brake Pad Inserts

$8.75

Kool-Stop’s Campi 2000 insert pad was designed to fit Campagnolo systems made after the year 2000.
Features:
— Patented Plow Tip
— Water Grooves
— Dove Tail fit
— Rim Friendly
— Replacement pads for Campagnolo 10-speed groups
Black: standard compound designed for dry condition riding
Dual: combination of Salmon and Black compounds for more controlled, smoother stopping
Carbon 2: updated formula for carbon rims, withstands steep descents with reduced wear
Ceramic: This compound was designed for ceramic coated rims and is great in all weather conditions.

Kool-Stop
Campi C89 Series Brake Pad Inserts

$6.95

Kool-Stop’s C89 Series insert pad was designed to fit in Campagnolo 8 and 9 speed group systems. Also fits Shimano Dura Ace BR-7400 and BR-7403.
Features:
— Patented Plow Tip
— Water Grooves
— Dove Tail fit
— Rim Friendly Compounds
Options:
— Black: Kool-Stop’s standard compound which is great for all weather conditions, but designed for dry condition riding.
— Salmon: Kool-Stop’s most famous Salmon compound is also one of our most aggressive compounds for extreme all weather conditions especially in the wet, but still superb in the dry.
— Dual: A fusion of Kool-Stop’s two finest compounds which will give superb braking in all weather conditions. This combination produces a more controlled smooth stop!

Kool-Stop
Dura-Type Brake Pad Inserts

$6.95 — $11.25

The Dura Type insert pad was originally developed as an aftermarket upgrade for high end Shimano brake systems. The Kool-Stop Dura pads are the same spec as Shimano pads and fit Shimano, SRAM, TRP and Tektro holders with a set screw.
Compounds:
— Black: Kool-Stop’s standard compound which is great for all weather conditions, but designed for dry condition riding.
— Ceramic: This compound was designed for ceramic coated rims and is great in all weather conditions.
— Salmon: Kool-Stop’s most famous Salmon compound is also one of the most aggressive compounds for extreme all weather conditions especially in the wet, but still superb in the dry.
— Carbon: Kool-Stop’s original carbon compound which works great for most carbon wheels but will wear quicker on fast steep descents.
— Dual: A fusion of Kool-Stop’s two finest compounds which will give superb braking in all weather conditions. This combination produces a more controlled smooth stop!
Features:
— Patented Plow Tip
— Water Grooves
— Rim Friendly Compounds
— Fits 55mm length holders

Brakes/Levers/Pads — New Spin Bicycle Shop

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Shimano
Altus BR-CT91 Cantilever Brake with Link Wire

$10.99

Shimano
BL-RS600 Disc Brake Lever For Flat Handlebar

$44.99

Shimano BL-RS600 Hydraulic Disc Brake Lever For Flat Handlebar.
Specifications:
— Application: Road, Cyclocross
— Type: hydraulic
Technical Information:
— Lever Length: 3-finger
— Adjustment Options: reach adjust (tool)
— Mount: clamp (split), I-Spec II
— Design: Rear Right, Front Left
— Brake Lever Material: aluminium
— Lever Body Material: aluminium
— Connection: straight
Features:
— for flat mount brakes
— I-Spec II compatible
— recommended brake caliper: BR-RS405
— funnel bleeding
— lever anodized, master cylinder painted
— stainless steel clamp bolt

Shimano
Deore XT BL-M8100/BR-M8120 Disc Brake and Lever

$229. 99

With a focus on reduced weight and cross-country tuned stopping power, Shimano Deore XT brakes provide intuitive modulation so that you can explore your limits with confidence. The levers feature an optimized lever axle position, refined ergonomics, and increased rigidity thanks to an additional handlebar contact point. The BR-M8120 4-piston calipers are designed for tough enduro trails and include heat-dissipating finned metal pads.
— 10% stiffer than previous generation M8000 even under high-temp conditions
— Quicker brake engagement with a shorter free stroke
— Tool-free reach adjustment
— Free stroke adjustment
— I-SPEC EV Clamp Band
— Brakes are pre-bled for convenient installation

Shimano
Deore XT SM-RT86 Disc Brake Rotor

$59.99

Shimano Deore XT SM-RT86 6-Bolt rotors feature a 3-layer construction with an aluminum core and two stainless steel outer layers. Reducing rotor surface temperature approximately 100 degrees Celsius compared to all-steel rotors, the result is better braking performance and reduced brake fade.
— Aluminum spider
— Includes rotor fixing bolts and locking washers

Shimano
J-Type Metallic Pads

$36.00

Shimano
R55C4 Road Brake Pads

$10.00 — $15.00

Shimano
SLX BR-M7100 Disc Brake with Lever

$136. 99

Shimano
SLX BR-M7120 Disc Brake with Lever

$186.99

Shimano
STEPS RT-EM810 Disc Brake Rotor for E-Bike Speed Sensor System

$64.99 — $69.99

Shimano RT-EM810 disc brake rotors deliver powerful and consistent braking performance in all riding conditions. The Ice Tech Freeza design significantly reduces heat build-up in the system to ensure consistent, high-performance braking even on the steepest downhill stretches. Shimano’s Center Lock mounting system makes installing and removing rotors quick and easy thanks to the spline mount and lock ring design.
— For use with E-Bike Speed Sensor systems
— Recommended Brake kit: M9120/M8120/M7120

Shimano
Ultegra 6800 Road Brake Shoe Set

$23. 00

Shimano Road brake shoe sets
— R55C4 pads
— Aluminum pad holder
— Color: Black
— Intended Brake Type: Caliper
— Pad Attachment Style: Bolt-In (Caliper)
— Pad Type: Cartridge
— Rim Compatibility: Standard

Shimano
XT BL-M8100/BR-M8120 Disc Brake and Lever

$229.99

Deore XT M8100 hydraulic disc brakes are designed to provide high-performance braking for a variety of MTB riding styles.
— BL-M8100 features a stiffer brake lever design that provides added support for aggressive riding
— Servo Wave Action technology means quicker brake engagement with shorter free stroke
— The BR-M8120 4-piston caliper is designed for tough enduro trails
— Set includes brake lever, caliper, finned metal pads, and hose
— Brakes are pre-bled for convenient setup

Shimano
XT M8100 Hydraulic Disc Brake

$169.99

The Deore XT M8100 hydraulic disc brake is designed to provide high performance braking for a variety of MTB riding styles. Includes the brake lever and disc brake caliper.
— BL-M8100 features a stiffer brake lever design that provides added support for aggressive riding
— Servo Wave Action technology means quicker brake engagement with shorter free stroke
— The BR-M8100 2-piston brake caliper is optimized for cross country riding styles
— Includes finned metal pads and hose
— Brake Caliper Type: Post Mount
— Hydraulic Hose Length: 1000mm (Front) / 1700mm (Rear)
— Hydraulic Fluid Type: Mineral Oil
— Rotor Included: No
— Pad Compound: Metallic

Shimano
XT SM-RT86 6-Bolt IceTech Disc Brake Rotor

$68.99

Shimano XT RT86 6-Bolt Disc Rotor
— 3-layer structure with aluminum core and two stainless steel outer layers reduces rotor surface temperature approximately 100 degrees Celsius compared to all-steel rotors
— Aluminum spider
— Includes rotor fixing bolts and non-turn washers
— Hub/Disc Compatibility: 6-Bolt Disc
— Weight: 173 g
— Rotor Size (mm): 203 mm
— Rotor Type: Two Piece
— Pad Compatibility: All Pad Compounds

Shimano
XTR RT-MT900 Disc Brake Rotor

$81. 99 — $87.99

SRAM
Trail/Guide Disc Brake Pads

$27.00 — $33.00

SRAM’s Disc Brake Pads are reliable and rugged. These pads are compatible with Avid Trail and SRAM Guide and G2 disc brakes.

Magura
9.P Disc Brake Pads

$34.02

9 Series Disc Brake Pads
— One piece connected back plate
— Performance compound offers excellent bite for strong braking response in a variety of conditions
— Pair of disc brake pads for one MT5, MT7 caliper

Magura
EBT screws

$17. 00

Replacement EBT screws close the bleed port on Magura brakes.
— Torque spec: 0.5 nM
— T25 head
— Sold as a pair

Magura
HS33/HS11 Compression Sealing Washer

$1.25

Magura hs33/hs11 compression sealing washer bag of 20
— Small parts used to install hydraulic hose for Magura disc brakes.
— Compatible with Campagnolo h21 brake/shift levers

Magura
Hydraulic Fittings

$5.00 — $26.53

— Attachment parts for Magura OEM and braided-stainless hydraulic disc and rim brake tubing

Magura
Olives

$1.50

Magura olives (compression ferrule) bag/20
— Small parts used to install hydraulic hose for Magura disc brakes.
— Compatible with Campagnolo h21 brake/shift levers

Kool-Stop
Steel Disc Pads (Shimano)

$18.99

— High performance compounds recommended for all-conditions
— Steel backing

Giant
Molded Canti Brake Pads

$9.99

-Molded cantilever brake pads

Giant
Molded U-Brake Pads-Threaded

$9. 99

-Molded threaded u-brake pads

Giant
Molded V-Brake Pads

$9.99

-Molded v-brake pads

Avid
BB7 MTN Cable Disc Brake Caliper

$65.00

The industry standard cable-actuated disc brake since its introduction is still popular due to smooth ball bearing operation and ease of installation and maintenance.
— All calipers have 74mm mounting bolt spacing
— For use with long cable-pull levers
— Pad retraction and spring tension are adjustable
— Includes steel-backed sintered pads
— Brake Caliper Type: Post Mount
— Brake Lever Actuation: Long Pull
— Hub/Disc Compatibility: 6-Bolt
— Rotor Included: No

Avid
Disc Brake Pads (Juicy/BB7/BB5)

$19.00 — $30.00

To keep your Avid brakes functioning properly, check your pads for wear and replace them when necessary. Organic compound pads are softer for quieter braking and increased modulation, while metallic pads dissipate heat better and last a bit longer. Two pads, one retraction spring and a mounting bolt are included (enough for one brake) in each pad set. And, choose an aluminum backing plate if you’re really counting the grams.

Simple mechanisms. Lever grade 7 online training at Rostelecom Lyceum

Introduction

In this lesson we will talk about simple mechanisms.

Simple Machines are devices by which work is done by mechanical energy alone. We are surrounded by devices that operate on electricity (see Fig. 1), due to the energy of fuel combustion, but this has not always been the case.

Fig. 1. Electric kettle

Previously, all the work could actually be done by hand, or with the help of animals, due to wind or water flow (mills), that is, due to mechanical energy (see Fig. 2).

Fig. 2. Old simple mechanisms

And simple mechanisms help in this, facilitate the work.

Our forces are limited, and this is a problem. For example, we cannot lift and move a ton of bricks from one place to another at a time. But we can spend more time, go more distance back and forth and move the bricks four at a time, or as many as we can carry. What about a screw that needs to be screwed into a tree? We cannot screw it with our bare hands. Screwing it in piece by piece, like a mountain of bricks brick by brick, is also impossible. You need to use a mechanism, a screwdriver. With it, we have to turn the screw a few turns so that it enters the tree at least a centimeter. But it is incomparably easier than by hand. nine0005

A simple mechanism — a shovel

Consider such a simple mechanism as, for example, a shovel. Of course, it makes the job easier, it is much easier to dig the ground with it than with your hands. We stuck the shovel into the ground. To raise a clod of earth, you need to press on the handle. Where will you push to make it easier? Experience suggests that it is necessary to press, that is, apply force, closer to the end of the handle (see Fig. 3).

Fig. 3. Choice of point of application of force

Try to apply force closer to the blade of the shovel, it will become much harder to lift the clod of earth. Applying the same strength, you will not lift anything. That is why shovels with a short handle, for example, sappers, are made with a small canvas: you still can’t lift a lot of earth with a short handle.

The shovel is a lever. A lever is a rigid body with a fixed axis of rotation (most often it is a fulcrum or suspension point). Forces act on it that tend to rotate it around the axis of rotation. In a shovel, the axis of rotation is the fulcrum on the upper edge of the hole (see Fig. 4). nine0005

Fig. 4. Axis of rotation of the shovel

A clod of earth, which we lift, acts with some force on the blade of the shovel, and our hands act on the handle with less force (see Fig. 5).

Fig. 5. Action of forces

Balance swing

Consider another example: everyone rode on a balance swing (see Fig. 6).

Fig. 6. Swing-balancer

This is also a lever: there is a fixed axis of rotation, around which the swing rotates under the influence of children’s gravity. nine0005

In order to outweigh your friend sitting on the opposite seat, to lift him, you will sit on the very edge of the swing. If you sit closer to the swing support, you can not outweigh it. Then you need to put someone adult and heavy in your place (see Fig. 7).

Fig. 7. The applied force must be greater than at the edge

At such a point of application of force, a greater force is needed than when the force was applied at the edge of the swing (see Fig. 8).

Fig. 8. Application of forces

Lever

Moreover, the force needed is as many times less, how many times the lever arm is larger. Lever arm is the distance from the fulcrum or suspension point of the lever to the point where the force is applied (see fig. 9).

Fig. 9. Lever arm and force

Forces will be applied perpendicular to the lever. nine0005

Direction of the force acting on the lever

In which direction will you act on the shovel to lift the earth? You will apply force to the shovel so that it wraps around the fulcrum, that is, perpendicular to the handle (see Fig. 10).

Fig. 10. Direction of force

If you act along the handle, it will not lift the earth, unless you pull the shovel out of the ground or stick it deeper. If you press on the handle at an angle, the force can be thought of as the sum of two forces: you push perpendicular to the handle and simultaneously push or pull along the handle (see Figure 11). nine0005

Fig. 11. Action of force along the handle

Only the perpendicular component will rotate the shovel.

So, we have a lever and two forces that act on it: the weight of the load and the force that we apply to lift this load. We have found that the longer the arm of the lever, the less force is needed to balance the lever. Moreover, how many times the lever arm is greater, the force is so much less. Mathematically, this can be written as a proportion:

It does not matter whether the forces are applied on opposite sides of the fulcrum or on the same side. In the first case, the lever was called the lever of the first kind (see Fig. 12), and in the second case, the lever of the second kind (see Fig. 13).

Fig. 12. Lever of the first kind

13. Lever of the second kind

Working with a shovel

We have seen how the shovel makes it easier for us to dig the ground. It rests on the edge of the formed hole in the ground, this will be the axis of its rotation. The weight of the earth is applied to the short arm of the lever, we apply force to the long arm of the lever with our hands (see Fig. 14). nine0005

Fig. 14. Application of forces to a shovel

Moreover, by how many times the lever arms differ, the forces applied to these arms differ by the same factor.

So, we lifted the clod of earth, but then we need to take the shovel with both hands, lift it completely and move the earth. Where do we take the handle of the shovel with the second hand? Everything is simple when we already know the principle of the lever. The second hand will become the new lever support. It must be placed in such a way as to again give a gain in strength, it must again divide the lever into short and long arms. Therefore, we will take the shovel as close as possible to the blade of the shovel. Try to lift the shovel by holding the edge with both hands — you may not succeed even with an empty shovel. nine0005

The principle by which the lever works is used very often. For example, pliers are a lever of the first kind (see Fig. 15). We act on the handles of the pliers with a force , and the pliers act on a piece of wire, tube or nut with a force much greater in modulus than . So many times more, how many times more:

Fig. 15. An example of a lever of the first kind

Another lever is a can opener, only now the application points are on one side of the fulcrum O. And again we apply force to the handle, and the opener blade acts on the tin of the can with a much greater force in modulus (see fig. 16). nine0005

Fig. 16. An example of a lever of the second kind

How many times greater than ? In the same amount, how many times more than:

You can get a huge gain in strength, we are limited only by the length of the lever and its strength.

Problem

Calculate how long the lever should be so that with its help a fragile girl weighing 50 kg could lift a car weighing 1500 kg by pressing on the lever with all her weight. Let’s place the fulcrum of the lever so that the short arm of the lever is 1 m (see Fig. 17). nine0005

Fig. 17. Picture for problem

The problem describes a lever (see Fig. 18).

Fig. 18. Condition of the problem 1

We know how many times the gain in force gives the lever:

Forces are applied on opposite sides of the lever support, so the two arms of the lever will sum up its length:

We described the process mathematically , specified in the condition. In our case, the force acting on the shoulder is the weight of the car, and the force acting on the shoulder is the weight of the girl. nine0005

Now all that’s left is to solve the equations and find the answer.

From the first equation we find the shoulder. The greater force is applied to the smaller lever arm, which means that this is the short arm equal to 1 m.

How does a shovel dig itself?

Considering the examples, we did not take into account the force of gravity acting on the lever.

Imagine that we have stuck a shovel shallowly into the ground. If the shovel is heavy enough, it will be able to lift a small mass of earth without our help, we will not even need to apply any force to the handle. The shovel will rotate around the axis of rotation under the action of gravity acting on the shovel handle (see Fig. 19).

Fig. 19. Rotation of a shovel around its axis

However, most often the weight of the lever is negligible compared to the forces that act on it, so in our model we consider the lever to be weightless.

Force and displacement

In the example of a girl and a car, we have seen that with the help of a lever we can do work that we would never have done without a lever. With the help of a lever, even the Earth could be moved, as Archimedes spoke of (see Fig. 20). nine0005

Fig. 20. Assumption of Archimedes

The problem is that there is nothing to rest the lever on, there is no suitable fulcrum. And you, of course, imagine what an unimaginable length such a lever must be, because the mass of the Earth is 5974 billion billion tons.

Everything works out too well: we can reduce the force necessary to do the work almost indefinitely. There must be a catch, otherwise with leverage our possibilities would be endless. What’s the catch? nine0005

Using a lever, we apply less force, but at the same time we make a greater displacement (see Fig. 21).

Fig. 21. Movement increases

We moved the shovel handle to the outstretched hand, but raised the earth only a few centimeters. Archimedes, if he still found a fulcrum, in his entire life would not have had time to turn his lever so as to move the Earth. The less force we apply, the more displacement we make. And the product of force and displacement, that is, work, remains constant. That is, the lever gives a gain in strength, but a loss in movement, or vice versa. nine0005

Levers that are used “in reverse”

Levers are not always used to do work with less force. Sometimes it is important to win in the move, even if it means applying more force. So does the fisherman who needs to pull the fish, move it a long distance. At the same time, he uses the fishing rod as a lever, applying force to its short shoulder (see Fig. 22).

Fig. 22. Using a fishing rod

Our hand is also a lever. The muscles of the arm contract and the arm bends at the elbow. At the same time, she can lift some load, do work. At the same time, muscles and loads act with some forces on the bones of the forearm (see Fig. 23).

Fig. 23. Our arm is a lever

The axis of rotation of the forearm is the elbow joint. Our entire musculoskeletal system consists of such levers. And the term “lever arm” itself is named so by analogy with the shoulder of one of the levers in our body — the arm. nine0005

Muscles are arranged in such a way that during contraction they cannot shorten by those half a meter by which we need to lift, for example, a cup of tea. You need to win in movement, so the muscles are attached closer to the joint, to the smaller arm of the lever. In this case, you need to apply more force, but for the muscles this is not a problem.

Incline

The lever is not the only simple mechanism that makes it easier for us to get the job done.

What simple mechanism do you use when you go up to the first floor? You can jump to the window if you can, and just climb into the room. We are accustomed to doing the same job of moving ourselves home much safer and easier — climbing stairs. So we make a greater path, but apply less force to ourselves. If we make a long gentle staircase, it will become even easier to climb, we will walk almost as if on a flat surface, but we will have to make a longer path (see Fig. 24). nine0005

Fig. 24. Sloping ladder

The inclined plane is a simple mechanism. It is always easier not to lift something heavy, but to drag it down a slope.

Consider how an ax splits wood. Its blade is pointed and expands closer to the base, and the deeper the wedge of the ax is driven into the wood, the wider it is distributed and eventually splits (see Fig. 25).

Fig. 25. Chopping wood

The principle of operation of the wedge is the same as for the inclined plane. To move the pieces of wood a centimeter apart would require enormous force. It is enough to apply less force to the wedge, however, it will be necessary to make a greater movement deep into the wood. nine0005

Screws work on the same inclined plane principle. Let’s take a closer look at the screw: the groove along the screw is an inclined plane, only wrapped around the screw shaft (see Fig. 26).

Fig. 26. The inclined plane of the screw

And we also drive the screw to the depth we need without much effort. At the same time, as usual, we lose in movement: we need to make many turns of the screw in order to drive it a couple of centimeters. In any case, it is better than pushing the wood and inserting a screw into it. nine0005

When we drive a screw with a screwdriver, we make our work even easier: the screwdriver is a lever. Look: the force with which the screw acts on the tip of the screwdriver is applied to the smaller arm of the lever, and we act on the larger arm with our own hand (see Fig. 27).

Fig. 27. How a screwdriver works

The handle of a screwdriver is thicker than the tip. If the screwdriver had handles like a corkscrew, the gain in strength would be even greater.

We use simple machines so often that we don’t even notice it. Let’s take an ordinary door. Can you name three uses for a simple mechanism in a door? nine0005

Note where the handle is. It is always located at the edge of the door, away from the hinges (see Fig. 28).

Fig. 28. Location of the handle on the door

Try to open or close the door by pushing it closer to the hinges, it will be difficult. The door is a lever, and in order to open the door with as little force as possible, the arm of this force should be as large as possible.

Let’s take a closer look at the pen itself. If it was a bare axle, it would be difficult to open the door. The handle increases the arm to which the force is applied, and we, applying less force, open the door (see Fig. 29).

Fig. 29. Door handle

Let’s look at the shape of the key. I think you can answer why they are made with wide heads. And why are the hinges on which the door rests not located next to each other, but about a quarter of the height from the edges of the door? Remember how we took a shovel when we picked it up — the same principle here. And you can also pay attention to the lock tongue cut at an angle, to the screws with which the door is screwed to the hinges (see Fig. 30).

Fig. 30. Door hinges

Results

As you can see, simple mechanisms underlie all kinds of devices — from a door and an ax to a crane. We use them unconsciously when we choose, for example, where to grab a branch to tilt it. Nature itself, when creating a person, used simple mechanisms when it created our musculoskeletal system or teeth with their wedge-shaped shape. And if you pay attention, you will notice many more examples of how simple mechanisms make mechanical work easier, and you can use them even more efficiently. nine0005

This concludes our lesson, thank you for your attention!

References

Sokolovich Yu.A., Bogdanova G.S. Physics: A Handbook with Examples of Problem Solving. – 2nd edition, redistribution. — X .: Vesta: Publishing house «Ranok», 2005. — 464 p.
Peryshkin A.V. Physics: Textbook Grade 7. – M.: 2006. – 192 p.

Additional Recommended Internet Links

Virtuallab. by (Source).
School.xvatit.com (Source).
Lena24.rf (Source).
Fizika.ru (Source).

Homework

What is a lever? Give a definition.
What examples of levers do you know?
The length of the smaller lever arm is 5 cm, the larger arm is 30 cm. A force of 12 N acts on the smaller arm. What force must be applied to the larger arm to balance the lever? nine0374

Simple mechanisms. Lever arm. Inclined plane. Blocks

Contents:

Lever arm.
Fixed block.
moving block.
Inclined plane.
The golden rule of mechanics.
mechanism efficiency.

nine0427

The author is a professional tutor, author of textbooks for preparing for the exam Igor Vyacheslavovich Yakovlev

Topics of the USE codifier: simple mechanisms, mechanism efficiency.

Mechanism is a device for converting force (increasing or decreasing it).
Simple mechanisms is a lever and an inclined plane.

Lever.

Lever is a rigid body that can rotate around a fixed axis. On fig. 1) shows a lever with an axis of rotation. Forces and are applied to the ends of the lever (points and ). The shoulders of these forces are equal, respectively, and .

The balance condition of the lever is given by the moment rule: , whence

Fig. 1. Lever

From this ratio it follows that the lever gives a gain in strength or in distance (depending on the purpose for which it is used) as many times as the longer leverage is longer than the smaller one. nine0005

For example, to lift a load of 700 N with a force of 100 N, you need to take a lever with an arm ratio of 7 : 1 and put the load on the short arm. We will win in strength by 7 times, but we will lose by the same amount in distance: the end of the long arm will describe a 7 times larger arc than the end of the short arm (that is, the load).

Shovel, scissors, pliers are examples of a lever that gives a gain in strength. The rower’s oar is a lever that gives a gain in distance. And the usual balance scales are an equal-armed lever that does not give a gain either in distance or in strength (otherwise they can be used to weigh buyers). nine0005

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Fixed block.

An important type of lever is block — a wheel fixed in a holder with a groove through which a rope is passed. In most problems, the rope is considered to be a weightless inextensible thread.

2 shows a fixed block, i.e. a block with a fixed axis of rotation (passing perpendicular to the plane of the figure through the point).

A weight is fixed at the right end of the thread at a point. Recall that the weight of the body is the force with which the body presses on the support or stretches the suspension. In this case, the weight is applied to the point where the weight is attached to the thread.

A force is applied to the left end of the thread at a point.

The shoulder of the force is , where is the radius of the block. The weight arm is equal to . This means that the fixed block is an equal-armed lever and therefore does not give a gain either in strength or in distance: firstly, we have equality, and secondly, in the process of movement of the load and the thread, the movement of the point is equal to the movement of the load. nine0005

Why, then, is a fixed block needed at all? It is useful in that it allows you to change the direction of effort. Usually a fixed block is used as part of more complex mechanisms.

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Moving block.

3 shows the movable block whose axis moves with the load. We pull the thread with a force that is applied at a point and directed upward. The block rotates and at the same time also moves upward, lifting a load suspended on a thread. nine0005

At the moment, the fixed point is the point , and the block rotates around it (it would «roll» over the point ). They also say that the instantaneous axis of rotation of the block passes through the point (this axis is directed perpendicular to the plane of the figure).

The weight of the load is applied at the point of attachment of the load to the string. The leverage is the same.

But the shoulder of the force with which we pull the thread turns out to be twice as large: it is equal to . Accordingly, the equilibrium condition for the load is equality (which we see in Fig. 3: the vector is two times shorter than the vector ). nine0005

Therefore, the movable block gives a gain in strength twice. At the same time, however, we lose the same two times in distance: in order to lift the load by one meter, the point will have to be moved by two meters (that is, pull out two meters of thread).

The block in fig. 3 has one drawback: pulling the thread up (behind the dot) is not the best idea. Agree that it is much more convenient to pull the thread down! This is where the fixed block comes to the rescue.

4 shows a lifting mechanism, which is a combination of a movable block with a fixed one. A load is suspended from the movable block, and the cable is additionally thrown over the fixed block, which makes it possible to pull the cable down to lift the load up. The external force on the cable is again indicated by the vector.

Fundamentally, this device is no different from the moving block: with its help, we also get a two-fold gain in strength. nine0005

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Inclined plane.

As we know, it is easier to roll a heavy barrel down an inclined walkway than to lift it vertically. Bridges are thus a mechanism that gives a gain in strength.

In mechanics, such a mechanism is called an inclined plane. Inclined plane is a smooth flat surface located at some angle to the horizon. In this case, they briefly say: «inclined plane with an angle». nine0005

Let’s find the force that must be applied to the mass load in order to lift it uniformly along a smooth inclined plane with an angle . This force, of course, is directed along the inclined plane (Fig. 5).

Select the axis as shown in the figure. Since the load moves without acceleration, the forces acting on it are balanced:

Designing for axle :

from where

This is the force that must be applied to move the load up the inclined plane.

To evenly lift the same load vertically, you need to apply a force equal to . It can be seen that since . The inclined plane really gives a gain in strength, and the greater, the smaller the angle .

Widely used types of inclined plane are wedge and screw.

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The golden rule of mechanics.

A simple mechanism may give a gain in strength or distance, but it cannot give a gain in work.

For example, a lever with a leverage ratio of 2 : 1 gives a gain in strength twice. To lift a load with a weight on the smaller arm, you need to apply force to the larger arm. But to raise the load to a height, the larger arm will have to be lowered by, and the work done will be equal to:

i.e. the same value as without using the lever. nine0005

In the case of an inclined plane, we gain in strength, since we apply a force to the load that is less than gravity. However, in order to raise the load to a height above the initial position, we need to travel along an inclined plane. At the same time, we are doing the work

, i.e. the same as when lifting the load vertically.

These facts serve as manifestations of the so-called golden rule of mechanics.

The golden rule of mechanics. None of the simple mechanisms gives a gain in work. How many times we win in strength, how many times we lose in distance, and vice versa. nine0005

The golden rule of mechanics is nothing more than a simple version of the law of conservation of energy.

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mechanism efficiency.

In practice, one has to distinguish between useful work A useful, which must be done with the help of a mechanism in ideal conditions without any losses, and complete work A full,
which is performed for the same purposes in a real situation.

Total work equals the sum:
— useful work;
— work performed against friction forces in various parts of the mechanism;
— work done to move the constituent elements of the mechanism.

Thus, when lifting a load with a lever, in addition, work must be done to overcome the friction force in the axis of the lever and to move the lever itself, which has some weight.

Complete work is always more useful. The ratio of useful work to full is called the coefficient of performance (COP) of the mechanism:

= A useful / A full

Efficiency is usually expressed as a percentage. The efficiency of real mechanisms is always less than 100%.

Calculate the efficiency of an inclined plane with an angle in the presence of friction. The coefficient of friction between the surface of the inclined plane and the load is .

Let the weight of the mass rise uniformly along an inclined plane under the action of a force from point to point to a height (Fig. 6). In the direction opposite to the movement, the sliding friction force acts on the load. nine0005

There is no acceleration, so the forces acting on the load are balanced:

Projecting on the X axis:

. (1)

Projecting on the Y axis:

. (2)

In addition,

, (3)

From (2) we have:

Then from (3):

Substituting this into (1), we get:

. nine0005

The total work is equal to the product of the force F and the path traveled by the body along the surface of the inclined plane:

A full =.

Useful work is obviously equal to:

A useful =.

For the desired efficiency, we get:

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