Due to some mechanical fault, a lift falls freely from the top of a multistory building. Which of the following is the apparent weight of a man inside the lift, if the mass of the man is 80 kg while the value of 'g' is 10 ms-2?
Correct answer: B. Zero
- A. 900 N
- B. Zero
- C. 800 N
- D. 700 N
Explanation
If the elevator falls freely, the downward acceleration of the man in the elevator is: a = g Now, the force exerted by the floor on the man is equal to the actual weight of the man minus the net upward force on him. F = ma - mg F = mg - mg F = 0 N Hence, the force exerted by the floor on the man is zero.
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