# Simple Machines - PowerPoint PPT Presentation

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Simple Machines. What is a Machine?. A machine is a device that helps us perform tasks. How are machines used?. change energy from one form into another transfer forces change the direction of a force change the magnitude of a force change distance or speed. Real simple machines.

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Simple Machines

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## Simple Machines

### What is a Machine?

• A machine is a device that helps us perform tasks.

### How are machines used?

• change energy from one form into another

• transfer forces

• change the direction of a force

• change the magnitude of a force

• change distance or speed

### Real simple machines

• 1. State the main function or functions of each of the following machines:

• (a) an axe

• (b) a tennis racket

• (c) a round doorknob

• (d) a screwdriver

• 2. Give two or three examples, of simple machines in the kitchen that increase the force you apply.

### Two Families

All machines can be grouped into two categories:

• The Lever Family

• The Inclined Plane Family

### Complex machines

• A machine that is composed of two or more simple machines

A lever is a rigid bar that can rotate freely around a support called a fulcrum.

Fulcrum

### The Lever Family

dL

dE

FL

FE

Fulcrum

Distance to the Effort

(mass) x 9.8

Force of the Effort

### First Class Lever

FL

FE

• In a first-class lever, the fulcrum is between the load and the effort force.

Examples include a shovel or pry bar

### Second Class Lever

FL

FE

• In a second-class lever, the load is between the fulcrum and the effort force.

Examples include a wheel barrow

### Third Class Lever

FL

FE

• In a third-class lever, the effort force is exerted between the fulcrum and the load.

Examples include a fishing rod