Work

Chapter 15 Section 4

Objectives

• Identify 6 simple machines• Explain how the machine work• Explain the difference between

classes of levers• Describe how pulleys work

Simple Machines

• An instrument that makes machines work easier

• Simple machines are divided into two categories

• Lever family• Inclined Plane family

Lever Family

• Simple Lever

Lever Family

• Pulley

Lever Family

• Wheel and Axle

Levers

• All levers have a rigid arm that Pivots or turns around this point. This point is called the fulcrum

• There are three classes of levers: first class, second class and third class.

• Levers are placed in these categories by the input, output and where the fulcrum is located.

Levers

• First Class: Hammer taking out a nail• The MA depends on where the fulcrum is located .

The fulcrum is between the input and output force

• Second Class: Wheelbarrow• The output force is between the fulcrum and the

input force. These levers multiply force, so MA is greater than 1

• Third Class: Forearm of a person• These levers multiply distance, so the MA is less than 1.

The input is located between the fulcrum and the output force.

Levers

Pulley

• Two types: Fixed pulley and moveable pulley

• Fixed Pulley: Has a MA of 1 which means it just changes the direction of the force.

• Movable pulley: has a MA of greater than 1.

• You can combine fixed and moveable pulley to have a great MA

Pulley

Wheel and Axle

• Made of lever and pulley connected to an axle.

• When a small input turns the wheel, the output is multiplied.

• This is because the axle is smaller than the wheel, so less distance is covered.

Wheel and Axle