6 In Fig B the pin P sliding without friction in the slotted bar OA moves with constant velocity vo along the horizontal x axis causing the bar OA to rotate in the vertical plane about the fixed axis through O For the particular instant when 0 30 find the force F that the pin exerts on the bar The following numerical data are given W 5 lb 1 20 in vo 30 ips Ans F 1 29 lb 9 A right circular drum of radius r and weight W rotating at 600 rpm is braked by the device shown in Fig C Develop a formula for the time t required to bring the drum to rest if the coefficient of friction between the drum and breaking bar is u The following data are given 4 ft a 2 5 ft r 15 in 0 25 W 400 lb and P 100 lb Ans t 12 2 sec WALL 12 10 A solid right circular drum of radius r 1 ft and weight W 32 2 lb is free to rotate about its geometric axis as shown in Fig D Wound around the circumference of the drum is a flexible cord carrying at its free end a weight Q 10 lb If the weight Q is released from rest a find the time t required for it to fall through the height h 10 ft b With what velocity v will it strike the floor Ans a t 1 275 sec b v 15 7 fps B 2 FIG B 7 A shaft of radius r rotates with constant angular speed in bearings for which the coefficient of friction is u Through what angle will it rotate after the driving torque is removed Ans 0 ro 4 g A 8 The wheel of a small gyroscope is set spinning by pulling on a string wound around the shaft Its moment of inertia is I 0 05 lb sec in and the diameter of the shaft on which the string is wound is 1 2 in If 30 in of string is pulled off with a constant force of 12 lb what angular velocity will be imparted to the wheel Ans 120 rad sec Q FIG C FLERES h