Sphere A has mass m and is moving with velocity v. It makes a head-on elastic collision with a stationary sphere B of mass 2m. After the collision their speeds (v_A, and v_B) are: A) 0, v/2 B) -v/3, 2v/3 C) -v, v D) -2v/3, v/3 E) none of these

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Quizplus · Accepted Answer

Momentum is conserved, so the total momentum before the collision is mv and after the collision is mvA + 2mvB. Since the collision is elastic, kinetic energy is also conserved, so 1/2mv^2 = 1/2mvA^2 + 1/2(2mvB)^2. Solving these two equations gives vA = -v/3 and vB = 2v/3.

Sphere a Has Mass M and Is Moving with Velocity