Centre of Mass 3 Question 13

16. A ball of mass 0.2kg rests on a vm/s vertical post of height 5m. A bullet of mass 0.01kg, travelling with a velocity vm/s in a horizontal direction, hits the centre of the ball. After the collision, the ball and bullet

travel independently. The ball hits the ground at a distance of 20m and the bullet at a distance of 100m from the foot of the post. The initial velocity v of the bullet is

(2011)

(a) 250m/s

(b) 2502m/s

(c) 400m/s

(d) 500m/s

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Answer:

Correct Answer: 16. (d)

Solution:

R=u2hg20=v12×510 and 100=v22×510v1=20m/s,v2=100m/s.

Applying momentum conservation just before and just after the collision

(0.01)(v)=(0.2)(20)+(0.01)(100)v=500m/s



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