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.

Answer 1

m= 10 kg,u= 0 (Since the dumb-bell falls from rest) Distance covered, s= 80cm = 0.8m a= 10 ms-2
From equation of motion, v2=u2+ 2as
v2= 0 + 2 × 10 × 0.8
= 16 = v = $\sqrt{16}$ = 4ms-1
Momentum of dumb-bell just before it touches the floor
p = mv = 10 × 4 = 40 kg-ms-1
When the dumb-bell touches the floor, its velocity becomes zero. Thus, the total momentum of the dumb-bell is transferred to the floor. Hence, the momentum transferred to floor = 40 kg-ms-1.