Question

A ball of mass 1 kg strikes a heavy platform, elastically, moving upward with a velocity of 5 m/s. The speed of the ball just before the collision is 100 m/s downwards. Then the impulse imparted by the platform on the ball is :-

• A. 15 N-s
• B. 10 N-s
• C. 20 N-s
• D. 30 N-s

Answer 1

The correct option is D 30 N-s

According to the problem the mass of the ball is $1kg$

The velocity of the ball initially is $5m/s$ and the speed of the ball before collision is $10m/s$

Therefore the total speed of the ball $=10+5=15m/s$

Now we know that impulse is the change in momentum of ball.

Therefore impulse $=15+15=30Ns$