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