Barron's 2nd Edition PT1 Q38

Barron's Book

38) This question requires us to find the maximum speed of the mass after the spring accelerates it. Friction is not mentioned, so we can neglect it. In this case, we can easily solve this question using the conservation of mechanical energy.

Where E is mechanical energy

Next, we'll set up equations to find E[A] and E[B].

Where U[S] is elastic potential energy, k is the spring constant, x is distance of spring compression, K is kinetic energy, m is mass, v is speed, and E is mechanical energy

Finally, we can plug in all values at point A and point B to solve for the speed at B.

Where v[max] is the max speed

Answer: B