SIMPLE MACHINES
Chapter 5 Notes
Machine A device that helps make work easier
Changes the size or direction of the force
Simple Machine – A type of machine that uses only one kind of motion to make work easier
Complex Machine – a combination of simple machines.
Six Simple Machines 1. Lever – a bar that pivots around a fixed
point (fulcrum)
1st Class – the fulcrum in between the input force and output force
input output
fulcrum
Levers continue: 2nd Class – the output
force is between the fulcrum and the input force.
3rd Class – the input force is between the fulcrum and the output force
inputoutput
fulcrum
fulcruminput
output
Force Distance Trade Off
What increases for work input must decrease for work output.
As force increases, distance decreases.
As force decreases, distance increases.
Mechanical Advantage
How much force a machine is applying for you.
MA = Output Force ÷ Input force
The larger the mechanical advantage, the easier a machine makes your work.
Mechanical Efficiency
Measures how much friction a machine has. More Friction equals less work output.
ME = (work output ÷ work input) 100
Measured as a percentage
Simple machines 2. Inclined Plane – ramp ( forms a right
angle)
Applies a smaller force over a longer distance
Simple Machines 3. Wedge – A double inclined plane
Ex: knife, doorstop, ax head
Simple Machines 4. Screw – an inclined plane, wrapped
around a cylinder
5. Wheel and Axle – a simple machine with two circular objects of different sizes.
Wheels with teeth
Simple Machine 6. Pulley – a grooved wheel that
holds a cable. Fixed Pulley – the pulley is attached
and changes the direction of the force only
Movable – increases force without changing direction
Block and Tackle – A fixed pulley and a movable pulley are used together for a greater mechanical advantage