Two blocks A and B, each of mass m, hang vertically with a light spring between them and a string above A. The system is initially in equilibrium. Just after the upper string is cut, the acceleration of A is:

Question

G1 Physics · Accepted Answer

Before cutting, the spring force supports B and therefore equals mg. Just after cutting the spring force is unchanged. On A both its weight mg and the spring force mg act downward, so net force=2mg and aₐ=2g downward. Option B.