Question

Classify the following into work done or work not done.
Standing with a load above the head.

Answer 1

Hint: To answer this question correctly we will 1st need to know what work done means. Then we will look at its definition, later we will answer whether the given example is an example of work done or work not done.

Complete answer:
Have you ever pushed a load? I’m sure you have applied sufficient force for the block to move. And have you observed that when you apply that force the load displaces from its original position to a new position ,and continues to move until the force that is being applied to it stops. This whole process is the meaning of work done.
To get a clear idea, let's look at its definition:
Definition: Work done in physics is the transfer of force from one body to another along a displacement
Well the mathematical definition would be : work done is the product of force applied and the displacement that occurs due to the applied force \[\left( {W = F.s} \right)\].
Where F is force and s is displacement,
Now let's look at the example mentioned above , it is given that the person is standing with a load on his head. To see if the work is done we need to consider two factors: force as well as displacement. In this example the person is standing still with no movement at all. The load that he has held on his head, definitely applies a force on him. As we see that even though force is applied there is no movement in any way we can say that work is not done.
Hence the answer to the above question is work is not done.

Note: do not get confused as, Just because we see transfer of energy it doesn’t mean that the work is done. In this example we see that force is applied on the head of the person standing. There’s also potential energy due to the load and that energy is being transferred to the person's head, but in spite of all this there is no movement shown by the person due to the force acting on him/her. Hence work is not done.