Question

What is the speed of a ball that is attached to a string and swings in a horizontal circle of radius 2.0 m with centripetal acceleration of 15 m/s²?

Answer 1

As we know, the centripetal acceleration is

$$a_c=\frac{v^2}{r},\\\space\\ v=\sqrt{a_cr}=\sqrt{15\cdot2}=5.48\text{ m/s}.$$