# law of conservation of momentum

## Solution to problems – class 9 – Set 1 Q 59

Problem Statement 59) A man wearing a bullet-proof vest stands still on roller skates. The total mass is 80 kg. A bullet of mass 20 grams is fired at 400 m/s. It is stopped by the vest and falls to the ground. What is then the velocity of the man ? Solution When both man […]

## Solution to problems – class 9 – Set 1 Q 58

Problem Statement 58) A heavy car A of mass 2000 kg travelling at 10 m/s has a head-on collision with a sports car B of mass 500 kg. If both cars stop dead on colliding, what was the velocity of car B ? Solution Say, velocity of B before collision be V m/s Initial momentum […]

## Solution to problems – class 9 – Set 1 Q 57

Problem Statement 57) A ball X of mass 1 kg travelling at 2 m/s has a head-on collision with an identical ball Y at rest. X stops and Y moves off. Calculate the velocity of Y after the collision. Solution Initial momentum of X = 1×2 kg m/s = 2 kg m/s …………….(i) After collision […]

## Solution to problems – class 9 – Set 1 Q 56

Problem Statement 56)A truck of mass 500 kg moving at 4 m/s collides with another truck of mass 1500 kg moving in the same direction at 2 m/s. What is their common velocity just after the collision if they move off together? Solution Total initial momentum = 500 x 4 + 1500 x 2 = […]

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