Find the elastic potential energy stored in each spring shown in figure (12-E8), when the block is in equilibrium. Also find the time period of vertical oscillation of the block.

Repeat the previous exercise if the angle between each pair of springs is 120^o initially.

The springs shown in the figure (12-E7) are all upstretched in the beginning when a man starts pulling the block. The can exerts a constant force F on the block. Find the amplitude and the frequency of the motion of the block.

The string, the spring and the pulley shown in figure (12-E9) are light. Find the time period of the mass m.

Solve the previous problem if the pulley has a moment of inertia I about its axis and the string does not slip over it.