Question

A 4.0 kg ball is swung at a constant speed in a vertical circle of radius 2.5 m. If the ball completes one revolution in 3.0 s, what is the tension in the rope at the top of the circle?

Answer 1

$$T=m\frac{v^2}{r}-mg\\T=m\frac{(2\pi r)^2}{rT^2}-mg \\T=m\frac{(2\pi )^2r}{T^2}-mg\\T=4\frac{(2\pi )^2(2.5)}{3^2}-4(9.8)=4.7\ N$$