# A mass is attached to one end of the steel ruler

A steel ruler is placed in a vertical position. A mass is attached to one end of the steel ruler and the other end fixed. When the mass is displaced slightly sideways and then released, the mass will begin to oscillate. In the first experiment, the mass is attached to the top of the ruler. In the second experiment, the mass is attached to the bottom of the ruler. In both experiments, the amplitude is nearly the same.

Consequently,

a) in the first experiment, the time period of oscillation is larger.
b) in the second experiment, the time period of oscillation is larger.
c) in both experiments, the time period of oscillation is the same.

Solution.

In the second experiment, an elastic force and a projection of the force of gravity along the line of the displacement have the same direction. However, in the first experiment, the forces have opposite directions. Therefore, in the first experiment, a return force is smaller and the time period of oscillation is larger.