Question

A small 700-gram ball on the end of a thin, light rod is rotated in a horizontal circle of radius 0.60 m .

a.

Calculate the moment of inertia of the ball about the center of the circle.

Express your answer using two significant figures.

b.

Part B

Calculate the torque needed to keep the ball rotating at constant angular velocity if air resistance exerts a force of 0.017 N on the ball. Ignore the rod's moment of inertia and air resistance.

Answer 1

a) The required moment of inertia of the ball about the center of the circle is, Im2 1-700x10-3 x(0.6)2 I 0.252 kg-m b) The required torque that keep the ball rotating at constant angular velocity is, 0.6x 0.017xsin (90) T 0.0102 N-m