Question

A stone of mass 0.6kg attached to a string of height 0.5m, is whirled in a horizontal circle at s constant speed. If the maximum tension (force) in the string is 30N force before it breaks. Calculate the maximum number of revolution it can make.

Answer 1

$$F=ma=\frac{mv^2}{r}$$ $$v=\sqrt{Fr/m}=\sqrt{30*0.5/0.6}=5\:\rm m/s$$ $$v=2\pi n r$$

$$r=v/(2\pi r)=5/(2\pi*0.5)=1.6\:\rm rev/s$$