Question

How much momentum will a dumbbell 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

  • force and laws of motion CBSE Class 9
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Answer

Mass of the dumbbell, m = 10 kg

Distance covered by the dumbbell, s = 80 cm = 0.8 m

Acceleration in the downward direction, a = 10 m/s2

Initial velocity of the dumbbell, u = 0

Final velocity of the dumbbell (when it was about to hit the floor) = v

According to the third equation of motion:

v2= u2 + 2as

v2= 0 + 2 (10) 0.8

v= 4 m/s

Hence, the momentum with which the dumbbell hits the floor is = mv

= 10 × 4 kg ms-1

= 40 kg ms-1

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