Simple Machines: Principles, Types, and Applications

Common Characteristics of Machines

• Involve a kind of motion.
• Involve a kind of force.
• Make a job easier to do.
• Need some kind of input to make them work.
• Produce some kind of output.

Basic Types of Motion

• Rotary: Going round and round.
• Oscillating: Swinging backwards and forwards.
• Linear: In a straight line.
• Reciprocating: Backwards and forwards in a straight line.

A machine is a device that helps make work easier to perform.

Mechanical Advantage Defined

Mechanical Advantage: When a machine takes a small input force and increases the magnitude of the output force, a mechanical advantage has been produced.

Conservation of Energy Principle

Conservation of Energy: No machine can produce more work than the amount of work that is put into the machine.

The Six Simple Machines

The six simple machines are: lever, wheel and axle, pulley, inclined plane, wedge, and screw.

Wheel and Axle

Wheel and Axle: A simple machine consisting of a large wheel rigidly secured to a smaller wheel or shaft, called an axle.

Pulley

Pulley: A grooved wheel that turns freely in a frame called a block. Pulleys are used to simply change the direction of a force or to gain a mechanical advantage, depending on how the pulley changes the direction of a force.

Test Your Knowledge: True or False

a) Levers are classified into first, second, and third class. They are simple machines because all of them let us balance a given resistance by applying a smaller force.

FALSE. Third-class levers are always at a mechanical disadvantage.

b) A fixed pulley is a system that always lets you lift a certain mass with a smaller force.

FALSE. A fixed pulley is a system that primarily changes the direction of a force.

c) An axe could be thought of as a sort of screw mechanism.

FALSE. An axe is a type of wedge.

d) If you want to move the Earth by applying a small force, you should locate a fulcrum as close as possible to where you apply the force.

FALSE. To move a large resistance with a small force, the fulcrum should be located far away from where you apply the force (closer to the resistance).

e) In the wheel and axle system shown below, the shorter the BF (Brake Force) is the handle, the easier it will be to lift the bucket.

FALSE. A longer handle (larger radius for the wheel) provides greater mechanical advantage, making it easier to lift the bucket.

Identify the Simple Machine

a) PULLEY: A rope, a wheel with a groove in it, and a weight make up this simple machine.

b) LEVER: This simple machine can be used to lift a weight. It has a fulcrum, or pivot point.

c) WEDGE: This simple machine can be used to cut or split a part.

d) SCREW: It is made up of an inclined plane wrapped around a cylinder, forming a circular ramp.