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Question
A metal plate of mass 200 gm is balanced in mid–air by throwing 40 balls/sec, each of mass 2 gm, vertically upwards from below. The balls rebound with the same speed with which they strike the plate. Find the velocity with which the balls strike the plate. (Take g=10 m/s2)
A metal plate of mass 200 gm is balanced in mid–air by throwing 40 balls/sec, each of mass 2 gm, vertically upwards from below. The balls rebound with the same speed with which they strike the plate. Find the velocity with which the balls strike the plate. (Take g=10 m/s2)
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Solution
The correct option is B 12.5 m/s
Considering downward as positive,
F=mg=nm(v−(−u))t=nm(v+u)t
⇒0.2×10=40×2×10−3×2v1
(v=u, given that balls rebound with the same speed)
⇒v=12.5 m/s
Considering downward as positive,
F=mg=nm(v−(−u))t=nm(v+u)t
⇒0.2×10=40×2×10−3×2v1
(v=u, given that balls rebound with the same speed)
⇒v=12.5 m/s
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