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Question
How much momentum will a dumb-bell of mass 10 kg transfer to the floor if it falls from a height of 80 cm? Take its downward acceleration to be 10 m s−2.
Solution
Mass of the bell (m) = 10kg
Initial velocity (u) = 0
And let the final velocity = v
Distance (s) = 80cm
= 0.8m
Acceleration (a) = 10ms2
Therefore, according to the third equation of motion
v2 = u2 + 2as
v2 = 0 + 2 × 10 × 0.8
v2 = 16
v = 4m/s
Hence, momentum = mv
= 10 × 4
= 40 kgm/s
Since the bell's momentum just before touching the floor is 40 kgm/s, the momentum transferred by the bell to the floor will be 40 kgm/s.
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