(Meriam and Kraige 6th ed. 6/89) The spool (ro = 0.2 m, ri = 0.075 m) has a mass of 25 kg and radius of gyration kG = 175 mm. Constant force T is applied at an angle 0 to a cord securely wrapped around the inner radius as %3D T. ro TI G shown. If T = 50 N, 0 = 30°, and friction coefficients with the ground surface us = 0.10 and p = 0.08, find the angular acceleration of the disk, the acceleration of its center of mass G, and the friction force which the surface exerts on the spool. Assume that the spool is initially at rest.

Calculate the horizontal force P required to push the 85-lb lawn mower at constant speed. The center of gravity of the mower is at G, and the coefficients of rolling resistance are 0.12 for the front wheels and 0.18 for the rear wheels.

A uniform plank is supported by a fixed support at A and a drum at B that rotates clockwise. The coefficients of static and kinetic friction for the two points of contact are as shown. Determine whether the plank moves from the position shown if (a) the plank is placed in position before the drum is set in motion; and (b) the plank is first placed on the support at A and then lowered onto the drum, which is already rotating.

The cone clutch transmits the torque C through a conical friction surface with cone angle . The inner and outer radii of the friction surface are a and b, respectively. The left half of the clutch is keyed to the shaft, and the right half drives a machine (not shown) through a gear attached to its outer rim. Assuming uniform pressure on the friction surface, show that the maximum torque that can be transmitted by the clutch is

Draw the FBD for the bar described in Prob. 5.1 if the bar is homogeneous of mass 50 kg. Count the unknowns.

The 320-lb homogeneous spool is placed on the inclined surface. Determine the vertical force P that is required to keep the spool in the position shown. Assume that there is enough friction to prevent slipping at A.

The force P applied to the brake handle enables the band brake to reduce the angular speed of a rotating drum. If the tensile strength of the band is 3800 lb, find the maximum safe value of P and the corresponding braking torque acting on the drum. Assume that the drum is rotating clockwise.

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O Week6 Friction_21-22.pdf ds/Week6_Friction_21-22.pdf 4. The mine car and its contents have a total mass of 6000kg and a centre of gravity at G. If the coefficient of static friction 10 kN Doo→ between the wheels and the 0.9 m • G tracks is u = 0.4 when the wheels are locked, find the normal force acting on the front wheels at B and the rear /0.15 m A 0.6 m 1.5 m- wheels at A when the brakes at both A and B are locked. Does the car move? [Ans. NA = 16.5 kN, Ng =42.3 kN, the car does not move] ily TWO WAY POWER 09889 NO MODE SETUP

The uniform cylindrical drum weighs 250 lbs and is supported by a frictionless roller at A and the frame at C. The coefficients of friction between the frame and the drum at C are as follows, static coefficient u: = 0.3 and kinetic coefficient uk = 0.25. If the drum is at rest, find M required to start the drum moving? For full credit show a labeled free-body diagram. 2' 30°