Simple Machines What are the 6 types of

Simple Machines

What are the 6 types of simple machines? • Inclined Plane • Flat, slanted surface

What are the 6 types of simple machines? • Wedge • Thick at one end, tapered to a sharp edge on the other

What are the 6 types of simple machines? • Screw • Inclined plane wrapped around a cylinder

What are the 6 types of simple machines? • Lever • Rigid bar that is free to rotate at a fulcrum (comes in different CLASSES depending upon where the fulcrum is located)

What are the 6 types of simple machines? • Wheel and Axle • Two circular objects fastened together that rotate on an axis

What are the 6 types of simple machines? • Pulley • Grooved wheel and axel with a rope/chain around it • Can be fixed or moveable

What is a compound (or complex) machine? • A machine made up of two or more simple machines.

Define / Describe WORK • Work is done when a force causes an object to move in the direction that the force is applied. • If there is no movement, there is no work • The formula for work is: W = F x D – The unit for work is Joules (J)

Work (practice) • To help rearrange the furniture in your classroom you exert a force of 20 N to push a desk 10 m. How much work do you do? • A hydraulic lift exerts a 12, 000 N force to lift a car 2 m. How much work does the lift do?

What is purpose of a machine? • To make work easier. • You put a force in (input force) • The machine puts a force out (output force)

How do machines make work easier? 1. They can change the amount of force (like a bat, which is a lever) 2. They can change the distance (ramp) 3. They can also change the direction to make lifting load easier (fixed pulley is example)

Mechanical Advantage • The number of times a force you exert is multiplied by the machine. • MA = Output Force ÷ Input Force

Mechanical Advantage • If you exert a force of 20 N on a can opener and the opener exerts a force of 60 N on the can, then what is the MA? • If you exert an input force of 20 N and the machine produces an output force of 10 N, then what is the MA?

Efficiency of Machines • A comparison of the output work to input work in percent • And ideal machine would have 100% efficiency, but some work is lost to friction, so actual efficiency is always less • Efficiency = output work ÷ input work × 100

Efficiency Practice • You cut the lawn with a hand lawn mower. You do 250, 000 J of work to move the mower. If the work done by the mower in cutting the lawn is 200, 000 J. What is the efficiency of the lawn mower?

Power • HOW FAST work is being done • The same amount of work done faster will produce more power • Power = work ÷ time

Power Practice! • A motor performs 300, 000 Joules of work in 5 s. What is the power produced by the motor?