Question

A man is standing on a platform of balance takes a quick step, then his weight:
(A) Decreases
(B) Increases
(C) Remains unchanged
(D) First increases then decreases

Answer 1

It is mentioned that the man takes a quick step, which means that the time for which there was a loss of contact from the platform would be very less and therefore insignificant.

Complete step by step answer:
For that we must understand how the balance works. A spring balance is used to measure the weight of a substance. Since the weight of a person is being measured who is larger in size, so we assume a digital balance is being used. A balance does not calculate the weight of the person directly, it actually calculates the contact force generated by the person due to his weight, and since we know that action force is equal to the reaction force, so we assume that the contact force generated will be exactly equal to the weight of the person. Therefore, all balances measure the contact force generated and show them as the weight of the substance or a person.
Now we know that balance measures the contact force generated by the person to calculate their weight, but the question arises whether the contact force changes when the person takes a quick step? Well the answer may be yes or no because when the step is being taken, the contact area from the platform becomes less and so the weight will increase and then when the step is completed, it will be back to normal, but this decrease in the weight is so small that it would hardly make any difference.
Hence, option (C) is the correct answer.

Note: If the step taken was not quick, then the change in contact force between the steps would be significant and then the answer would have been D i.e. it will first increase and then decrease.