A student swings a 0.35 kg rock on a 1.25 m string above their head. The rock goes through 1 complete revolution in 0.665 s. What is the tension in the string?

39.0 N

Explanation:

Since the rock is in uniform circular motion, the tension in the string provides the centripetal force required to keep the rock in circular motion.

So we can write:

where

T is the tension in the string

m = 0.35 kg is the mass of the rock

r = 1.25 m is the radius of the circle (the length of the string)

is the angular velocity of the rock

Here the rock covers 1 revolution in a time of

t = 0.665 s

1 revolution corresponds to an angle of rad, so the angular velocity is:

Therefore substituting into the previous equation, we can find the centripetal force, which is the tension in the string:

the displacement produced by the body.  

the amount of force subjected to the body.  

the angle between the direction of force and displacement