A machine is any tool or device that enables us to do work easily, quickly and conveniently.
A simple machine is a tool that allows us to use less force to do work. There are seven types of simple machines.1. Inclined plane
An inclined plane makes the job of moving loads from the lower to higher area or vice versa easier. For instance, pushing a heavy box to a higher area needs less effort than carry it up.
A screw has ridges called thread, cut around it in the form of a spiral and special kind of inclined plane. When a turning force is applied to the head of the screw, the spiral edge of the screw travels a longer distance. This implies that the force was applied over quite a long distance to make the screw moves forward at a very small distance.
Wheels with notches and cogs, cut around the edge is called gears. Each gear is fitted to another gear to transfer movement in a machine. A gear is also used to changed the direction and speed of a movement.
A pulley is made up of wheel with groove round a rim of the pulley which holds a rope. A rope or pulley does not increase the lifting force but it only changes the direction of force. The force of pulling is equal to the weight of the load.
A lever is a rigid bar or rod or plank that can swing around a support to transmit and magnify a force which is used to lift a load. The support or point on which the lever turns is called fulcrum. The object that the lever lifts or moves is called load. The force that is exerted on the lever is called effort.
When one or two incline planes are put together, back to back, it forms a wedge. A wedge changes the direction of a force and increases the effort. For example, using a sharp knife to cut sweet potato. As the knife moved downwards it creates a strong sideways force that spilts it open.
7. Wheel and axle
Wheel is a cylindrical object or circular object that rotates about the axis of the cylinder. The axle is a rigid rod that goes throught the centre of the wheel and lies along the culinder axis. When the two are combined together, it is called a wheel and axle.
wheel and axle
roda dan gandar
Before ending this lesson, let' s do some tests.
TEST B - MACHINES
For each of the following complex machine, tick (√) the simple machines found in them.
Simple machines found in them
L = Lever
WA = Wheel and axle
IP= Inclined plane
P = Pulley
S = Screw
W = Wedge
G = Gears
A pair of scissors
A manual can opener
A lawn mover
A hand drill
A hole puncher
A step ladder
A tower crane
Have a good try!