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A piano is rolling down a frictionless slope at an ever increasing speed. The piano tuner sees it, slowing it down to a constant speed. The magnitude of the force on the man by the piano is F MP ; the magnitude of the force on the man by the man is F PM . If we compare these forces, we find (A) F PM > F MP always. (B) F PM > F MP while the piano slows down but F PM = F MP when the piano is moving at constant speed. (C)F PM = F MP always. (D) F PM = F MP while the piano slows down but F PM MP when the piano is moving at constant speed.

A piano is rolling down a frictionless slope at an ever increasing speed. The piano tuner sees   it, slowing it down to a constant speed. The magnitude of the force on the man by the piano  is FMP; the magnitude of the force on the man by the man is FPM. If we compare these forces, we find
(A) FPM > FMP always.
(B) FPM > FMP while the piano slows down but FPM = FMP when the piano is moving at            constant speed.
(C)FPM = FMP always.
(D) FPM = FMP while the piano slows down but FPM MP when the piano is moving at              constant speed.

Grade:upto college level

1 Answers

Deepak Patra
askIITians Faculty 471 Points
8 years ago
The correct option is (B) FPM > FMP while the piano slows down but FPM = FMP when the piano is moving at constant speed.
The piano starts to decelerate when it is slowing down. At this time, the applied force by the piano tuner on piano (FPM) is greater than the force due to piano on the piano tuner (FMP). But when the piano is moving at a constant speed, the acceleration of the piano is zero and the net force on the piano will be zero. So, when the piano is moving at a constant speed, applied force by the piano tuner on piano (FPM) is equal to the force due to piano on the piano tuner (FMP)
Therefore, FPM > FMP while the piano slows down but FPM = FMP when the piano is moving at a constant speed.
From the above observation we conclude that, option (B) is correct.

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