3. A small 650g ball on the end of a thin lightweight rod is rotated in a horizontal circle of radius 1.2m. Calculate a. the moment of inertia of the ball about the center of the circle (.94) b. the torque needed to keep the ball rotating at constant angular velocity if air resistance exerts a force of .02N on the ball. Ignore the rod's mass and air friction. (2.4 x 10-2) 4. A merry go round accelerates from rest to .68 rad/s in 24s. Assuming the ride is a uniform disk of radius 7 m and mass of 31000Kg, calculate the net torque required to accelerate it. (2.2 x 104)10-5 and 10-6 Rotational Dynamics 31. (I) Determine the moment of inertia of a 10.8-kg sphere of radius 0.648m when the axis of rotation is through its center. (T)29 (II) The bolts on the cylinder head of an engine require tightening to a torque of 75 m . N. If a wrench is 28 cm long, what force perpendicular to the wrench must the mechanic exert at its end? If the six-sided bolt head is 15 mm across (Fig. 10-49), estimate the force applied near each of the six points by a socket wrench. 28 cm 15 mm F on wrench VF on bolt FIGURE 10-49 Problem 29