A body of mass 2 kg moving at 3 m s-1 collides and sticks to a stationary body of mass 4 kg. The common velocity after impact is
Correct answer: B. 1 m s-1
- A. 0.5 m s-1
- B. 1 m s-1
- C. 1.5 m s-1
- D. 2 m s-1
Explanation
Momentum is conserved, so the initial momentum of 2 times 3, which is 6 kg m s-1, is shared by the combined mass of 6 kg, giving a velocity of 1 m s-1. This is a perfectly inelastic collision, so kinetic energy is not conserved even though momentum is. Only the moving body contributes momentum, since the other starts at rest.
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About Collisions
Collisions involve the conservation of linear momentum when bodies interact for a short time. The topic covers impulse, elastic and inelastic collisions, kinetic energy changes, and the coefficient of restitution, with calculations usually based on one dimensional motion. Momentum remains conserved in isolated collisions, but kinetic energy is conserved only in elastic collisions.
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