1. Warm Up #1
What are simple machines?

2. Ch. 12 Energy, Work, and Simple Machines
Lesson 3: Machines

3. Essential Questions What are simple machines?
In what ways can machines make work easier?

4. Simple Machines
Machines transfer mechanical energy from one object to another
Simple machines – machines that do work using one movement
Don’t change the amount of work required
Do change the way work is done

5. Inclined plane – a flat, sloped surface
Ex: ramp
Brainpop – Inclined planes
Screw – an inclined plane wrapped around a cylinder
Ex: screw-top bottle (soda bottle)
Wedge – an inclined plane that moves
Ex: pizza cutter, knives

6. Lever – a simple machine that pivots around a fixed point
Ex: tab of a can, scissors
Brainpop - Levers
Wheel and Axle – a shaft attached to a wheel of a larger diameter so that both rotate together
Ex: doorknob, car’s steering wheel
Brainpop – Wheel and Axle
Pulley – a grooved wheel with a rope or cable wrapped around it
Ex: flagpole
Brainpop - Pulley

7. Complex Machines – 2 or more simple machines working together

8. Machines and Work Work you do on a machine is input work
Ex: window washer pulling rope
Work the machine does on an object is output work
Ex: distance he
moves

9. Efficiency – the ratio of output work to input work
Efficiency is never 100% as some work is transformed into wasted thermal energy due to friction
To improve efficiency, reduce friction between moving parts