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Force And Machines
Simple Machines
A thing that helps us to do something faster or easier is called simple machine. Simple machines are the lever, the pulley, the inclined plane and the wheel and axle. We shall learn about them one by one.
Figure 7.8
Lever
Lever is a simple machine which is usually a long rod. Lever is mostly used for lifting heavy loads by applying a smaller force (Figure 7.8). The rod is pivoted at a point that is called fulcrum. One end of rod is placed under the load to be lifted, while a downward force is applied on the other end to lift the load. Levers are all around us. Some examples of lever are scissors, nut cracker, wheel barrow and human arm (Figure 7.9)
Figure 7.9 Examples of lever
Pulley
Pulley is another simple machine which is used for changing the direction of force and moving the things up or down. A pulley is used for drawing water out of a well. It is also used in cranes for lifting heavy loads (Figure 7.10).
Figure 7.10 Examples of pulley
Inclined Plane
It is also a simple machine. The inclined plane is simply a ramp, with the help of which we can move things from lower to higher places or higher to lower places easily. Usually, ramps are used to load the heavy objects on the trucks (Figure 7.11). They are also used in hospitals to carry patients to upper storey’s conveniently and comfortably without using stairs.
Figure 7.11 Use of inclined planes
Wheel and Axle
Wheel is the major invention in the history of mankind. Wheel does not work without axle. Axle is a rod passing through the centre of the wheel. It allows the wheel to turn around it. Wheel combined with the axle forms a simple machine “wheel and axle” which changes sliding motion into axle have many uses in our daily life. A few are shown in the Figure 7.13.
Figure 7.12 Merry-go-round is an example of wheel and axle
Figure 7.13 Use of wheel and axle