Warm Up #1 What are simple machines?

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

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

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

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

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

Complex Machines – 2 or more simple machines working together

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

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