FORM 2-TOPIC 5-PHYSICS-SIMPLE MACHINES .
SIMPLE MACHINES
A simple machine is a non-powered mechanical device that changes the direction or magnitude of a force. In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. A simple machine uses a single applied force to do work against a single load force. Ignoring friction losses, the work done on the load is equal to the work done by the applied force.
A lever is a rigid body, which when used turns about a fixed point called a fulcrum or pivot. It is used to shift heavy loads.
The Three Classes of Levers
Identify the three classes of levers
Classes of Levers
There are three classes of levers:
- First class lever
- Second class lever
- Third class lever
First Class Lever
Is the class lever whereby the pivot is between load and effort. Examples of first class levers are: see-saw, crowbar, pair of scissors and claw hammer.
First Class Lever
Second Class Lever
Is the class lever where by load is between pivot and load. eg, wheel barrow, tongs, nutcracker, bottle opener.
Second Class Lever
Third Class Lever
Is the class lever whereby Effort is between load and pivot. Eg, fishing load.
Third Class Lever
The Mechanical Advantage, Velocity Ratio and Efficiency of Lever
Determine the mechanical advantage, velocity ratio and efficiency of lever
Mechanical Advantage of Lever
M.A =X/Y
M.A =Load arm/Effort arm
Levers in Daily Life
Use of levers in daily life
The reason for a lever is that you can use it for amechanical advantagein lifting heavy loads, moving things a greater distance or increasing the speed of an object.
- Increase force:You can increase the applied force in order to lift heavier loads.
- Increase distance moved
- Increase speed: You can increase the speed that the load moves with Class 1 or Class 3 levers.
