Machines

Making Work Easier

What Is A Machine?

A machine is a device that makes work easier

Examples

1. Doorknob

2. Pencil Sharpener

3. Knife

4. Crow Bar

5. Axe

Simple Machines

Simple machines are devices that do work with only one movement

There are six types of simple machines:1. Levers2. Pulleys3. Wheel and axle4. Inclined plane5. Wedge6. Screw

Pictures

Advantages of Simple Machines

They help us overcome friction and gravity

A crowbar could help us move a heavy rock or pry the lid off a wooden crate

Machines make work easier by changing the force you exert in size, direction or both

Effort and Resistance Forces

The force applied to the machine is called the effort force (Fe)

The force applied by the machine to overcome resistance is called the resistance force (Fr)

Forces cont.

Sketch

Two Kinds of Work

There is work done on the machine (Win)

There is also work done by the machine (Wout)

Win=Fexde

Wout=Frxdr

Ideal Machine

If there was a perfect machine with out energy being lost to friction and heat then work input would equal work output

perpetual machines - Google Search

The Lever

A lever is a simple machine that consists of three parts:

1. An effort arm

2. A Resistance arm

3. A fulcrum

Sketch in Notes

Fulcrum

Effort Arm

Resistance Arm

Levers

There are three kinds of levers

1. 1st class

2. 2nd Class

3. 3rd Class

1st Class Lever

The 1st class lever has the fulcrum in the middle of the two arms

Examples are the see-saw, can openers, and scissors

Sketch

2nd Class Levers

2nd class levers have the resistance and effort arms on one end, and the fulcrum on the other. The resistance is in the middle here

Sketch

3rd Class Levers

The 3rd class has the fulcrum on one end and the arms on the other, except reversed. Now the effort arm is in the middle

Sketch

Pulley’s

A pulley is like a 1st class lever There is a fulcrum in the middle (the

wheel) and a resistance rope and effort rope

Pulleys can be fixed or movable

Fixed pulley

Movable Pulley

Block and Tackle

Compound Machines

A machine made up of several simple machines make up a compound machine

Examples are a bicycle, a lawnmower, or a pencil sharpener