Question

What is the magnitude of the centripetal force that must be applied in order for a 2kg ball on a 2.0 m string to spin with uniform circular motion at 5.0 m/s

Answer 1

The ball needs to accelerate with a magnitude a (pointed towards the center of the circle) of

a = (5.0 m/s)² / (2.0 m) = 12.5 m/s²

Then the required tension F in the string would need to be

F = (2 kg) (12.5 m/s²) = 25 N

Answer 2

because centripetal force equals mv^2/r, we can plug in our known values to result in (2(5)^2)/2, which is equal to 25 n.