A string 0.5 ~m long is used to whirl a 1 ~kg stone in a vertical circle at a uniform velocity of 5 ~m ~s ⁻¹ . What is the tension in the string when the stone is at the top of the circle?

Step-by-step solution

The centripetal force needed to keep the stone moving at 5 ~m ~s ⁻¹ is F_c= m v^2 r = (1 ~kg ) (5 ~ms ⁻¹ )^2 0.5 ~m =50 ~N The weight of the stone is W=m g=(1 ~kg ) (9.8 ~m ~s ⁻² )=9.8 ~N . At the top of the circle, T=F_c-W=50 ~N -9.8 ~N =40.2 ~N