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Question

A car of mass 400 kg travelling at 72 kmph crashes a truck of mass 4000 kg and travelling at 9 kmph in the same direction. The car bounces back with a speed of 18 kmph. The speed of the truck after the impact is
  1. 9 kmph
  2. 18 kmph
  3. 27 kmph
  4. 36 kmph

A
9 kmph
B
18 kmph
C
27 kmph
D
36 kmph
Solution
Verified by Toppr

Using momentum conservation,

mcarucar+mtruckutruck=mcarvcar+mtruckvtruck

400×72+4000×9=18×400+4000×v

v=18 kmph

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