Concept explainers
Boxes A and B are at rest on a conveyor belt that is initially at rest. The belt is suddenly started in an upward direction so that slipping occurs between the belt and the boxes. Knowing that the coefficients of kinetic friction between the belt and the boxes are
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Chapter 12 Solutions
Vector Mechanics For Engineers
- To unload a bound stack of plywood from a truck, the driver first tilts the bed of the truck and then accelerates from rest. Knowing that the coefficients of friction between the bottom sheet of plywood and the bed are μs= 0.40 and μk= 0.30, determine (a) the smallest acceleration of the truck which will cause the stack of plywood to slide, (b) the acceleration of the truck which causes corner A of the stack to reach the end of the bed in 0.9 s.arrow_forwardA small 250-g collar C can slide on a semicircular rod which is made to rotate about the vertical AB at a constant rate of 7.5 rad/s. Knowing that the coefficients of friction are μs = 0.25 and μk = 0.20, indicate whether the collar will slide on the rod if it is released in the position corresponding to (a) 0= 75°, (b) 0 = 40°. Also, determine the magnitude and direction of the friction force exerted on the collar immediately after release.arrow_forwardA spring AB of constant k is attached to a support at A and to a collar of mass m. The unstretched length of the spring is 1 . Knowing that the collar is released from rest at x=x0 and neglecting friction between the collar and the horizontal rod, determine the magnitude of the velocity of the collar as it passes through point C.arrow_forward
- A truck is traveling down a road with a 4-percent grade at a speed of 60 mi/h when its brakes are applied to slow it down to 20 mi/h. An antiskid braking system limits the braking force to a value at which the wheels of the truck are just about to slide. Knowing that the coefficient of static friction between the road and the wheels is 0.60, determine the shortest time needed for the truck to slow down.arrow_forwardA bowler projects an 8-in.-diameter ball weighing 12 lb along an alley with a forward velocity v0 of 15 ft/s and a backspin ω0 of 9 rad/s. Knowing that the coefficient of kinetic friction between the ball and the alley is 0.10, determine (a) the time t1 at which the ball will start rolling without sliding, (b) the speed of the ball at time t1, (c) the distance the ball will have traveled at time t1arrow_forwardDetermine the maximum theoretical speed that may be achieved over a distance of 70 m by a car starting from rest, knowing that the coefficient of static friction is 0.80 between the tires and the pavement and that 60 percent of the weight of the car is distributed over its front wheels and 40 percent over its rear wheels. Assume a four-wheel drive car. The maximum theoretical speed that may be achieved is ____ km/h.arrow_forward
- In the braking test of a sports car its velocity is reduced from 70 mi/h to zero in a distance of 170 ft with slipping impending. Knowing that the coefficient of kinetic friction is 80 percent of the coefficient of static friction, determine (a) the coefficient of static friction, (b) the stopping distance for the same initial velocity if the car skids. Ignore air resistance and rolling resistance.arrow_forwardA small 250-g collar C can slide on a semicircular rod which is made to rotate about the vertical AB at a constant rate of 7.5 rad/s. Determine the three values of 0 for which the collar will not slide on the rod, assuming no friction between the collar and the rod.arrow_forwardKnowing that the coefficients of friction between the component I and member BC of the mechanism of Prob. 12.62 are μk = 0.35 and = 0.25, determine (μk a) the maximum allowable constant speed VB if the component is not to slide on BC while being transferred, (b) the values of 0 for which sliding is impending.Reference to Problem 12.62:arrow_forward
- Please answer this NEATLY, COMPLETELY, and CORRECTLY for an UPVOTE. In the system shown, a 150 N collar-pulley assembly slides on a horizontal shaft with coefficient of kinetic friction μk = 0.10 between the collar and the shaft, and is acted upon by a force P with a magnitude of P = 253.5 N at an angle θ = 30.35° as shown. Knowing that the assembly is initially at rest, what is the time when the velocity reaches to 3 m/s? Also, at this instant, find the tension in the cord and the velocity of block A.arrow_forwardThe system shown is at rest when a constant 150-N force is applied to collar B. Neglecting the effect of friction, determine (a) the time at which the velocity of collar B will be 2.5 m/s to the left, (b) the corresponding tension in the cable.arrow_forwardA 2000-kg automobile starts from rest at point A on a 6° incline and coasts through a distance of 150 m to point B. The brakes are then applied, causing the automobile to come to a stop at point C , which is 20 m from B . Knowing that slipping is impending during the braking period and neglecting air resistance and rolling resistance, determine (a) the speed of the automobile at point B, (b) the coefficient of static friction between the tires and the road.arrow_forward
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