Work is said to have been done when force is used to move an object through a distance.
We use machines to help us to do work. This is because machines make work easier.
The work done by a machine depends on two things:
We will investigate two types of simple machines:
inclined planes and single fixed pulleys.
image of inclined planes and single fixed pulleys.
Any flat surface can be referred to as a plane.
When a plane is placed at an angle, it is said to be inclined. Inclined planes are sometimes called ramps or slopes.
It is easier to walk up a gentle slope than a steep slope.
This is because when walking up a gentle slope, we are lifting our bodies only a short height each time we take a step, hence using less energy.
Examples of inclined planes include ramp, wedge, ladder, screw, staircase and road winding uphill.
Images of two types of staircases.
Paths that lead up a hill are either zigzag or spiral.
This helps to reduce the slope of the hill.
This is also a type of inclined plane.
Screws are used for joining pieces of wood together when making furniture.
A screw is an example of an inclined plane.
The screw-type car jack is used for lifting cars up when changing a wheel.
Imagine lifting a car yourself to fix the wheel.
Is it possible?
A wedge is an example of a double-edged inclined plane.
Wedges can be used for various purposes.
For example, an axe used for splitting wood or cutting down big trees is an example of a wedge.
The metal part is in form of a wedge.
-In a single fixed pulley the load distance is equal to the effort distance.
When the load moves 1 metre the effort also moves1 metre.
When the load is 10 kg you require an effort of 10 kg to move it.
-The direction of the load is opposite to that of the effort.
When the load moves up, the effort moves down.
The advantage of this is that the direction of the effort has been changed by the pulley.
This way the total amount of work required to lift the load is reduced.
It is therefore more convenient to use a pulley than carry a load without a pulley.
Image of someone drawing water using a bucket with a string tied and using a pulley.
Staircases are often used to move from one floor to another in a multi-storey building.
A ladder is a structure made up of two long straight pieces of wood or metals joined by cross bars as shown below. The crossbars are called rungs. How does a ladder help to make work easier?
Climbing a wall using a ladder is easier than climbing without. A ladder makes the work of climbing the wall easier.
A pulley is a simple machine that makes work easier by changing the direction and point at which a force works.
Pulleys are wheels with grooves on which ropes move.
A single fixed pulley helps to make work easier by changing the direction of force to make it more convenient.
Instead of pulling the rope upwards, you pull it downwards yet the load continues to be lifted upwards.
Other areas where single- fixed pulleys are used include