Question

A 4 kg object attached to a horizontal string moves with constant speed in a circle on a frictionless horizontal surface. The kinetic energy of the object is 72 J and the tension in the string is 426 N. Find the radius of the circle. Answer in units of m

Answer 1

r = 0.338 m

Step-by-step explanation:

Mass = m = 4 kg

T = 426 N

K.E= 1/2 m V²

⇒V² = 2 * K.E/m

⇒ V² = 2 * 72 / 4

⇒ V² = 36

⇒ V = 6 m/s

Now

Fc = mV²/ r

⇒ r = mV²/Fc

Fc = T ( According to Newton's 3rd law)

⇒ r = mV²/ T

⇒ r = 4 * 6²/ 426 m

⇒ r = 0.338 m