A 1 kg object moving to the right at 6 m/s strikes a 2 kg object at rest. Immedi

Question

A 1 kg object moving to the right at 6 m/s strikes a 2 kg object at rest. Immediately after the collision, the 1 kg object moves to the left with a speed of 2 m/s and the 2 kg object moves to the right with a speed of 4 m/s. Which of the following statements best describes the collision? (A) The collision is elastic because the total momentum of the system is constant. (B) The collision is elastic because the total momentum and kinetic energy of the system are constant. (C) The collision is inelastic because the total momentum of the system is not constant. (D) The collision is inelastic because the total kinetic energy of the system is not constant.

Explanation / Answer

The collision is not inelestic because speed of both objects is not same after collision.

Let's see,

consider right side - positive

lnitial moment = m1v1 + 0 = 1*6 = 6 kg.m/s

final momentum = m1v1 + m2v2 = -1*2 + 2*4 = 6 kg.m/s

We can see that momentum is conserved.

Now, lets see whether the KE is constant or not.

KEi = (1/2)m1v1^2 = 18 J

KEj = (1/2)*1*2^2 + (1/2)*2*4^2 = 18 J

Kinetic energy is also conserved.

So, the answer is (B)

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