A certain string can withstand a maximum tension of 42. N
without breaking. A child ties a 0.44 kg stone to one end and,
holding the other end, whirls the stone in a vertical circle of
radius 0.91 m, slowly increasing the speed until the string breaks.
(a) Where is the stone on its path when the string breaks (top of
the circle, middle of the circle or bottom of the circle)? (b) What
is the speed of the stone as the string breaks?