A Block of Mass M Is Initially Moving to the Right

Multiple Choice

A block of mass m is initially moving to the right on a horizontal frictionless surface at a speed v. It then compresses a spring of spring constant k. At the instant when the kinetic energy of the block is equal to the potential energy of the spring, the spring is compressed a distance of:

A)
B) (1/2) mv²
C) (1/4) mv²
D) mv²/4k
E)