See video [mediaplayer avi - 3.4MB]
[quicktime -
0.5MB] [ipod -
1.3MB]

A ball of mass
is attached to a light inextensible string of
length
. The ball is whirled around so that it moves in a
horizontal circle with constant angular speed
. Find
the angle
between the string and the vertical.
Show that the angle
is given by
. Now
increase the angular velocity. What happens to the ball? What
is the smallest angular velocity with which the ball can whirl in a
circle on the end of the string in this way?