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0.800 and k = 0.600.  Assuming that the weight is evenly distributed on the four wheels, calculate the maximum torque that can be exerted by the engine on a driving wheel, without spinning the wheel.  If you wish, you may assume the car is at rest.

33.Suppose the car in Problem 32 has a disk brake system.  Each wheel is slowed by the friction force between a single brake pad and the disk-shaped rotor.  On this particular car, the brake pad contacts the rotor at an average distance of 22.0 cm from the axis.  The coefficients of friction between the brake pad and the disk are

s = 0.600 and k = 0.500.  Calculate the normal force that the pad must apply to the rotor, in order to slow the car as quickly as possible.

Section 10.7  Relationship between Torque and Angular Acceleration

34.A grinding wheel is in the form of a uniform solid disk of radius 7.00 cm and mass 2.00 kg. It starts from rest and accelerates uniformly under the action of the constant torque of 0.600 N·m that the motor exerts on the wheel. (a) How long does the wheel take to reach its final operating speed of 1 200 rev/min? (b) Through how many revolutions does it turn while accelerating?

35.A model airplane with mass 0.750 kg is tethered by a wire so that it flies in a circle 30.0 m in radius. The airplane engine provides a net thrust of 0.800 N perpendicular to the tethering wire. (a) Find the torque the net thrust produces about the center of the circle. (b) Find the angular acceleration of the airplane when it is in level flight. (c) Find the linear acceleration of the airplane tangent to its flight path.

36.The combination of an applied force

and a friction force produces a constant total torque of 36.0 N·m on a wheel rotating about a fixed axis. The applied force acts for 6.00 s.  During this time the angular speed of the wheel increases from 0 to 10.0 rad/s.  The applied force is then removed, and the wheel comes to rest in 60.0 s.  Find (a) the moment of inertia of the wheel, (b) the magnitude of the frictional torque, and (c) the total number of revolutions of the wheel.

37.A block of mass m1 = 2.00 kg and a block of mass m2 = 6.00 kg are connected by a massless string over a pulley in the shape of a solid disk having radius R = 0.250 m and mass M = 10.0 kg.  These blocks are allowed to move on a fixed block-wedge of angle = 30.0 as in Figure P10.37. The coefficient of kinetic friction is 0.360 for both blocks.  Draw free-body diagrams of both blocks and of the pulley.  Determine (a) the acceleration of the two blocks, and  (b) the tensions in the string on both sides of the pulley.

Figure P10.37

38.A potter's wheel—a thick stone disk of radius 0.500 m and mass 100 kg—is freely rotating at 50.0 rev/min. The potter can stop the wheel in 6.00 s by pressing a wet rag against the rim and exerting a radially inward force of 70.0 N. Find the effective coefficient of kinetic friction between wheel and rag.

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