Question

A heavy ball of mass m is tied to a weightless thread of length l. The friction of the ball against air is

Answer 1

It can easily be seen that the ball attains the equilibrium position at an angle a of deflection of the thread from the vertical, which is determined from the condition

During the oscillatory motion of the ball, it will experience the action of a constant large force

and a small drag force (Fig. 148). Consequently, the motion of the ball

will be equivalent to a weakly attenuating motion of a simple pendulum with a free-fall acceleration g' given by

The period of small (but still damped) oscillations of the ball can be determined from the relation