Question

a 1 kg stone tied at the end..

Answer 1

Mass of the stone, m = 0.25 kg

Radius of the circle, r = 1.5 m
Number of revolution per second, n = 40 / 60 = 2 / 3 rps
Angular velocity, ω = v / r = 2πn
The centripetal force for the stone is provided by the tension T, in the string, i.e.,
T = FCentripetal
= mv2 / r = mrω = mr(2πn)2
= 0.25 × 1.5 × (2 × 3.14 × (2/3) )2
= 6.57 N
Maximum tension in the string, Tmax = 200 N
Tmax = mv2max / r
∴ vmax = (Tmax × r  / m)1/2
= (200 × 1.5 / 0.25)1/2
= (1200)1/2 = 34.64 m/s
Therefore, the maximum speed of the stone is 34.64 m/s.