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.

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

The 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

⇒  p = mv

⇒ p = 10 × 4

⇒ p = 40 kg m s-1