A0.25-kg ball attached to a string is rotating in a horizontal circle of radius 0.5m. assume the tension force is directed horizontally.
if the ball revolves twice every second, what is the tension in the string?

T= 19.74 N

Explanation:

The tension in the string will be equal to centripetal force on the ball. (Newton's 3rd law, equal acting and reacting forces acts on a body)

T = Fc

Fc = m w ²r

here:

m = 0.25 kg, r = 0.5 m

w = 2 rps = 2 * 2π rad/s      ( ∴ 1 revolution = 2π radians )

w = 4π rad/s

Fc = m w ²r = 0.25 * ( 4π )² * 0.5 N

Fc = T = 19.74 N

T= 19.74 N