the body of mass 17 kg is attached to a string of length of 3.4 m is whirled round in vertical circle .if the tension in the string at the lowest point is 300N .calculate the speed of the body​

The body is accelerating upward toward the center of the circle it traces out with magnitude

a = v ² / R

where

v = linear speed of the body

R = 3.4 m = radius of the circle it traces/length of the string

The only forces acting on it at the lowest point are the tension T of the string pulling upward on the body and weight W = mg of the body pulling it downward. By Newton's second law, we have

∑ F = T - mg = ma

Replace the acceleration with the expression from earlier and solve for v :

300 N - (17 kg) g = (17 kg) v ² / (3.4 m)

v ² = ((3.4 m) 300 N - (17 kg) g) / (17 kg)

v = √[ ((3.4 m) 300 N - (17 kg) g) / (17 kg) ]

v ≈ 5.16527 m/s ≈ 5.2 m/s