A bullet of mass 10 g moving horizontally with a velocity of 400 m s - 1 strikes a wooden block of mass 2 kg…

A bullet of mass 10 g moving horizontally with a velocity of 400 m s-1 strikes a wooden block of mass 2 kg which is suspended by a light inextensible string of length 5 m. As a result, the centre of gravity of the block is found to rise a vertical distance of 10 cm. The speed of the bullet after it emerges out horizontally from the block will be
  1. 100 m s-1
  2. 80 m s-1
  3. 120 m s-1
  4. 160 m s-1

Solution

CM rises through height h, so its velocity after collision =2gh
Apply conservation of linear momentum.
0.01×400=2×2gh+0.01×v
⇒v=120 m/s

Asked in: NEET 2016 (Phase 2)

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