A block of mass m=0.1 kg is connected to a spring of unknown spring constant k. It is compressed to a distance x from its equilibrium position and released from rest. After approaching half the distance (2x) from the equilibrium position, it hits another block and comes to rest momentarily, while the other block moves with a velocity 3m s−1. Find the total initial energy of the spring.
a. 0.3 J
b. 0.6 J
c. 0.8 J
d. 1.5 J