A man wanted to lift a rock occupying space on his farm. He has only a log to work with. What type of simple machine will he use and demonstrate how it makes his work easier?

Lever

Explanation:

That simple machine is lever made by using the log available there.

The working of this machine has been explained with the help of the diagram attached.

Let the force applied by man is F in the downward direction as shown in the figure.

Let be the torque due to force F about the fulcrum, so

Fa in the anti-clockwise direction.

Note that, the maximum force the man can apply is mg, where m is the mass of the body of the man.

Let M be the mass of the rock, so, the weight of the rock, W, is equal to the force due to gravity which acts in the downward direction. i.e

W=Mg

Let bet the torque about the fulcrum due to the weight of the rock, so

in the clockwise direction.

Here, the distances a and d are shown in the figure.

For lifting the rock, the torque applied by the man, , must be greater than the torque due to the rock, .

So, the lifting condition is

Here, the force, F, can be changed by varying the lengths and by relocating the position of the fulcrum.

In this way, the man can lift the rock by applying force F with the help of the lever, the simple machine made by using the available log.

b.transmitters send radio waves, and receivers capture radio waves.