Lesson 3: Machines - 7th Grade Science

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 Dont 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, cars 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

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