二. 計算題 (每題二十五分)
A block of mass M is connected to a spring of mass m and oscillates in simple harmonic motion on a horizontal, frictionless track. The force constant of the spring is k, and the equilibrium length is L. Find (a)(10%) the kinetic energy of the system when the block has a speed v, and (b)(10%) the period of oscillation. (Hint: Assume that all portions of the spring oscillate in phase and that the velocity of a segment dx is proportional to the distance x from the fixed end)