Question

Give five examples of zero work.

Answer 1

Step1: Zero work

1. When force and displacement are perpendicular to one another or when either the force or displacement is zero, zero work is defined.
2. If a block is moving on a smooth horizontal surface, no work is done.
3. We can explore a zero work example, the only requirement is that the force exerted be perpendicular to the displacement. Work will be done, but the perpendicular force will cancel it out.

Step2: Formula used

$W=fs\cos \theta [whereW=wrok,F=force,s=displacement,\theta =anglebetweenforceanddisplacement]$

Step3: Deriving zero work

When the angle between the force applied and the displacement is ${90}^o$, then the work done will be,

$$\begin{gathered} W=Fs\cos \theta \\ W=Fs\mathrm{co}s{90}^o[\mathrm{co}s{90}^o=0] \\ W=0 \end{gathered}$$

Thus, the value of work done will be zero and this work is called the “zero work”.

Step4: Five examples of zero work.

1. If you push a wall and it doesn't move, you haven't accomplished anything. Man pushing the vertical wall. (The force applied by the man will be perpendicular).
2. Sleeping for numerous hours is another example of not working. Because there is no change in displacement as well as there is no change in kinetic energy while you are sleeping.(The gravitational force will be perpendicular).
3. If you are carrying a bag and not moving, you are not getting any work done. Your hands exert a force on the bag to counteract the gravitational force, but since the bag is not displaced, the work done by you (your force) and gravity are both zero. As, the normal force or the gravitational force acting downwards. This force acts perpendicular to the surface of the earth.
4. Raman is a coolie who lifts a bundle of wood on his head for 30 minutes before becoming exhausted. There is no work done here on the bundle of wood.
5. The displacement of a person running forward on a horizontal surface.(the gravitational force will b perpendicular)