Question

39. In which case, work done will be zero? (a) A weight-lifter while holding a weight of 100 kg on his shoulders for 1 min (b) A locomotive against gravity is running on a level plane with a speed of 60 kmh (c) A person holding a suitcase on his head and standing at a bus terminal (d) All of the above​

Answer 1

Answer:

In case A = Work Done is Zero

So Option A is correct.

Explanation:

(a) A weight-lifter while holding a weight of 100 kg on his shoulders for 1 min

In the above case the Weight is not moving with respect to time. And the "weight lifter is only holding the Weight". So there is not any Work being done.

Answer 2

Work done by the body is given by= Force (F) × Displacement (d)

• a) A weight-lifter, while holding a weight of 100 kg on his shoulders for 1 min, has zero displacements. Hence, the word done by the weight-lifter is zero.
• b)A locomotive against gravity is running on a level plane with a speed of 60 km has zero work done as it has no displacement along or opposite to the direction of gravity.
• c)There is no change in the man's position or the suitcase. Hence the displacement is zero. The work done by the person is also zero.
• The correct answer would be an option (d)  All of the above​.