A 6' В 8' Problem 6/12 Representative Problems 6/13 The uniform pole of length l and mass m is placed against the supporting surfaces shown. If the coeffi- cient of static friction is us determine the maximum angle 0 at which the pole can be placed before it begins to slip. 0.25 at both A and B, Ans. 0 = 59.9° A 105° В Problem 6/13 14'

A 6' В 8' Problem 6/12 Representative Problems 6/13 The uniform pole of length l and mass m is placed against the supporting surfaces shown. If the coeffi- cient of static friction is us determine the maximum angle 0 at which the pole can be placed before it begins to slip. 0.25 at both A and B, Ans. 0 = 59.9° A 105° В Problem 6/13 14'

International Edition---engineering Mechanics: Statics, 4th Edition

4th Edition

ISBN:9781305501607

Author:Andrew Pytel And Jaan Kiusalaas

Publisher:Andrew Pytel And Jaan Kiusalaas

Chapter7: Dry Friction

Section: Chapter Questions

Problem 7.40P: The 60-lb plank rests on a frictionless roller at A, and the 20-lb triangular support BD. Both...

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The single-threaded screw of the floor jack has a pitch of 0.5 in. and a mean radius of 1.75 in. The angle of static friction is 8.5. (a) Determine the couple C that must be applied to the screw to start lifting a weight of 4000 lb. (b) What is the couple required to start lowering the weight?
The two uniform sheets of plywood, each of length L and weight W, are propped as shown. If the coefficient of static friction is 0.5 at all three contact surfaces, determine whether the sheets will remain at rest.
The square-threaded screw with a pitch of 10 mm and a mean radius of 18 mm drives a gear that has a mean radius of 75 mm. The static and kinetic coefficients of friction between the gear and the screw are 0.12 and 0.06, respectively. The input torque applied to the screw is C0=10Nm. Assuming constant speed operation, determine the output torque C1 acting on the gear.
The 40-lb spool is suspended from the hanger GA and rests against a vertical wall. The center of gravity of the spool is at G and the weight of the hanger is negligible. The wire wound around the hub of the spool is extracted by pulling its end with the force P. If the coefficient of static friction between the spool and the wall is 0.25, determine the smallest P that will extract the wire.
The panel of weight W with its center of gravity at G is placed between vertical guides and released. Determine the largest height h for which the panel will not slide down due to binding at corners A and B. The coefficient of static friction between the panel and the guides is 0.5.
The screw of the clamp has a square thread of pitch 0.16 in. and a mean diameter of 0.6 in. The coefficient of static friction between the threads is 0.4. Determine (a) the torque C0 that must be applied to the screw in order to produce a 28-lb clamping force at A; and (b) the torque required to loosen the clamp.
The mass of the unbalanced disk is m, and its center of gravity is located at G. If the coefficient of static friction is 0.2 between the cylinder and the inclined surface, determine whether the cylinder can be at rest in the position shown. Note that the string AB is parallel to the incline.
The leather rein used to fasten the horse to the hitching rail weighs 3.5 oz per foot. The coefficient of static friction between the rail and the rein is 0.6. If a 34-lb force acting on the bridle is sufficient to restrain the horse, determine the smallest safe length L for the free end of the rein.
The 60-lb plank rests on a frictionless roller at A, and the 20-lb triangular support BD. Both bodies are homogenous. The coefficients of static friction are 0.4 at B and 0.3 at D. Determine the largest force P that can be applied to the plank without initiating motion.
The uniform bar of weight W is supported by a ball-and-socket joint at A and rests against a vertical wall at B. If sliding impends when the bar is in the position shown, determine the static coefficient of friction at B. [Hint The direction of impending sliding is tangent to the dashed circle (the potential path of motion of point B).]
The coeffient of static friction between the uniform bar AB of weight W and the ground is 0.45. Find the smallest angle and the corresponding force P that would initiate simultaneous tipping and sliding of the bar.
The screw of the carjack has a pitch of 0.1 in. and a mean radius of 0.175 in. Note that the ends of the screw are threaded in opposite directions (right- and left-handed threads). The coefficient of static friction between the threads is 0.08. Calculate the torque C0 that must be applied to the screw in order to start the 1200-1b load moving (a) upward; and (b) downward.