Question

How much work is done on a ball of mass 100g to give it a momentum of 5 kg m s ^ -1?.

Answer 1

Answer:

consider a ball of mass m striking the plate with velocity v. The momentum with which the bullet strikes the plate is mv (take upward direction of momentum as positive). Since the bullet rebounds with the same velocity, the momentum of the bullet just after it rebounds is -mv. Change in momentum of this bullet is -2mv (final minus initial momentum). If n bullets are fired per second then change in momentum of the bullets per second is -2nmv. The momentum transferred to the plate per second is then 2nmv which is also the force on the plate by Newton’s second law.

In equilibrium the weight of the plate equals the force exerted by the bullets, i.e.

2nmv = Mg where M is the mass of the plate.

Or v = Mg/(2nm)

Now in your question, M = 200 g = 0.2 kg, n = 40. If mass m of the bullet is known, v can be found.

Explanation:

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Answer 2

Answer:

The mass of the ball =100g

=100/1000kg. =1/10 kg

The momentum

mass ×velocity=5kg m/s

velocity=0.5 m/s

Work done =change in momentum

=1/2 mv²-1/2mu²

=1/2mv²-0( u=0)

=1/2×1/10×1/2×1/2 J

=1/80 J

=0.0125 J

The work done is 0.0125 J

Hope this helps you friend