Wheels & Axles and Pulleys – Lesson Summary

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Learning Objective

In this lesson we will learn how wheels and axles and pulleys provide mechanical advantage.

Learning Outcomes

By the end of this lesson you will be able to:

  • Describe a wheel and axle and explain how it provides mechanical advantage.
  • Discuss how a wheel and axle can be considered as a lever.
  • Explain how wheels and axles can be force multipliers or speed multipliers, with examples.
  • Describe a pulley and explain how it provides mechanical advantage.
  • Compare fixed pulleys, movable pulleys and compound pulleys.
  • Discuss how a pulley can be considered as a lever.

 
wheels & axles and pulleys lesson contents

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Lesson Topics

1 | Wheels and Axles as Simple Machines

2 | Rotational Speed and Linear Speed

3 | Wheels and Axles as Force Multipliers and Speed Multipliers

4 | Wheels and Axles as Levers

5 | Mechanical Advantage of Wheels and Axles

6 | Pulleys as Simple Machines

7 | Fixed Pulleys, Movable Pulleys and Compound Pulleys

8 | Pulleys as Levers

9 | Mechanical Advantage of Pulleys

10 | Summary

Lesson Summary

  • A wheel and axle consists of a circular structure, known as the wheel, attached to a shaft or rod, known as the axle.
  • The wheel and the axle have the same rotational speed but different linear speeds.
  • When a wheel causes an axle to rotate:
  • The wheel and axle functions as a class 2 lever.
  • The wheel and axle is a force multiplier.
  • When an axle causes a wheel to rotate:
  • The wheel and axle functions as a class 3 lever.
  • The wheel and axle is a speed multiplier.
  • For a wheel and axle that is a class 2 lever, mechanical advantage is given by the formula:
  • mechanical advantage formula wheel and axle class 2 lever summary
  • Mechanical advantage will always be greater than 1.
  • For a wheel and axle that is a class 3 lever, mechanical advantage is given by the formula:
  • mechanical advantage formula wheel and axle class 3 lever summary
  • Mechanical advantage will always be less than 1.
  • A pulley is a special type of wheel and axle that consists of a rope or other material that passes around the outer surface of the wheel.
  • A fixed pulley is a pulley that stays in the same position.
  • It functions as a class 1 lever.
  • Fixed pulleys always have a mechanical advantage of 1.
  • They do not increase a force, but do change its direction.
  • A movable pulley is a pulley that moves with a load.
  • It functions as a class 2 lever.
  • Movable pulleys always have a mechanical advantage of 2.
  • They increase a force, but do not change its direction.
  • A simple pulley consists of a single wheel.
  • Its mechanical advantage depends on whether it is a fixed or movable pulley.
  • A compound pulley consists of two or more wheels connected by a single rope.
  • Its mechanical advantage is equal to the total number of rope sections that are supporting individual pulleys.

 
water pipe valve wheel

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