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Year 9 NSW
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Force and motion
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Machines
Topic : Machines
In this topic you will learn...
Chapter 1 :
Machines: speed and force multipliers
A machine is a device that makes work easier by transmitting or transforming energy
Machines have been used since ancient times
Machines are currently used for a huge number of tasks
Machines can decrease the force necessary to move an object or increase its speed
Machines can also change the direction in which force must be applied to do work
Simple machines consist of only one machine, such as a lever or pulley
Complex machines consist of many smaller machines
Chapter 2 :
Levers
A lever is a machine that consists of a bar or plane pivoting on a fulcrum
All levers have a load, a fulcrum and an effort
Levers work under the principle of conservation of energy
In a first class lever, the fulcrum is located between the load and the effort
In a second class lever, the load is located between the fulcrum and the effort
First and second class levers are force multipliers
In a third class lever, the effort is located between the fulcrum and the load
Third class levers are speed multipliers
Chapter 3 :
Inclined planes, wedges and screws
Inclined planes, wedges, and screws are related types of force multipliers
An inclined plane, or ramp, is an even surface that is tilted at an angle
Inclined planes reduce the force needed to move by increasing the distance moved
Inclined planes work because energy is conserved
Wedges are inclined planes that are moved through another object
Screws are inclined planes that rotate around a central point
Chapter 4 :
Wheel and axle
Wheels are circular objects that spin around a central shaft, called an axle
Wheels and axles use rotary motion
Wheels can work as speed multipliers when a large force is applied to the axle
Wheels are used as speed multipliers in cars and fans
Wheels can work as force multipliers when a small force is applied to the rim
Wheels are used as force multipliers in windmills and doorknobs
Gears are wheels with interlocking teeth that transfer motion
Gearing up is used in situations where higher speed is needed
Gearing down is used in situations where higher force is needed
Chapter 5 :
Pulley
A pulley is a wheel with a grooved edge where an object like a rope can be held
Pulleys can change the direction or magnitude of effort
A single pulley attached to a fixed point changes the direction of effort
Single pulleys attached to a fixed point do not change the magnitude of the effort
A fixed pulley working with a movable pulley can decrease the force to lift an object
Pulleys are slowed by friction
A system with two or more pulleys is called a block and tackle or chain hoist
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