What is work?How does it occur?

The result when a force moves an object a certain distance.

Simple Machines

Identify various types of systemsIdentify the purpose, inputs and

outputs of various systems

A “machine” is anything that reduces or changes the direction of the force that must be applied to move any object

Complex machines such as a cars are made up of many simple machines as

well as non-machine components such as electronics

Force:AnyPushOr Pull

Ancient Culture Machines

An inclined plane is a flat surface set at an angle (other than a right angle) against a horizontal surface. An inclined plane is a simple machine with no moving parts. It is simply a straight slanted surface.

The wedge is like an inclined plane. Actually, a wedge is two inclined planes joined together back to back. Examples of a wedge are an ax, the point of a nail, a doorstop, and a knife.

An inclined plane wrapped around a cylinder is another type of simple machine called the screw.

A pulley is a rope, belt, or chain wrapped around a grooved wheel. Pulleys can be fixed or moveable. The pulley is actually a variation of another simple machine...the lever.

A wheel and axle is a simple machine made up of two circular objects of different size. The axle (a small wheel) is attached to the center of a larger wheel. All wheels need an axle. The wheel and axle must move together to be a simple machine. A wheel and axle lifts or moves loads.

A lever is a rigid bar that rests on a fulcrum (a fixed point.) Something or someone must put force (push or pull) on a lever to make it work. The farther the force is from the fulcrum, the easier it is to work the lever. Levers may change the direction as well as the amount of force. There are three classes (kinds) of levers.

“Low Tech” Mechanical Systems

Any system that contains at least one simple system could be correctly described

as a machine.

LeversClass 1

Claw hammerSee-saw

Class 2

Nut crackerBottle opener

Class 3 Tweezerstongs

Machines make tasks

easier to perform!

Fulcrum (pivot point of a lever) is in the middle

Load force (force that the input force has to overcome in order to cause movement) is in the middle

Input force (effort applied to the lever) is in the middle

Simple or Complex?Page 34 Figure 12

Figure a Both Figure b

Lever to turn gear Features gears and simple machines

Pulley system

The combination of simple machines makes them complex machines... Or does it?

“All machines are simple machines.”Do you agree or disagree?

Check your learning...Simple Machine Example How society uses it to make life easier

Inclined plane

Wedge

Screw

Lever

Wheel and axle

pulley

Which of the following simple machines do you feel has the greatest effect on humans:

The inclined planeThe lever

The wheel and axle?Page 35

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