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You have been hired as an expert witness in a case involving an injury in a factory. The attorney who hired you represents the injured worker. The worker was told to lift one end of a long, heavy crate that was lying horizontally on the floor and tilt it up so that it is standing on end. He began lifting the end of the crate, always applying a force that was perpendicular to the top of the crate. As the end of the crate got higher, at a certain angle, the bottom of the crate slipped on the floor, and the worker, in trying to recover, stepped forward and the crate landed on his foot, injuring it badly. As part of your investigation, you go to the factory and measure the coefficient of static friction between a crate and the smooth concrete floor. You find it to be 0.340. Prepare an argument for the attorney showing that it was impossible to lift the crate in the manner described without it slipping on the floor.
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Chapter 12 Solutions
Physics for Scientists and Engineers
- A 215-kg robotic arm at an assembly plant is extended horizontally (Fig. P14.32). The massless support rope attached at point B makes an angle of 15.0 with the horizontal, and the center of mass of the arm is at point C. a. What is the tension in the support rope? b. What are the magnitude and direction of the force exerted by the hinge A on the robotic arm to keep the arm in the horizontal position? FIGURE P14.32arrow_forwardA person is standing on a section of uniform scaffolding as shown in the figure. The section of scaffolding is L = 1.50 m in length, has a ms = 24.5 kg mass and is supported by three ropes as shown. Determine the magnitude of the tension in each rope when a person with a weight of Wp = 640 N is a distance d = 0.700 m from the left end. magnitude of T1 N magnitude of T2 N magnitude of T3 Narrow_forwardA uniform horizontal beam 10.0 m long and a mass of 82 kg is attached to support cables on either end. The cable on the left end makes an angle of 120 with x-axis and the cable on the right end makes an angle of 30̊ with the x-axis. If a person of mass 82 kg stands 7 m from the right end, find (a) the magnitude of the tensions TL and TR in the cables.arrow_forward
- To get up on the roof, a person with a mass m = 71 kg leans an aluminum ladder (mass 10.5 kg and length 6.0 m) against the house on a concrete pad with the base of the ladder 2.00 m from the house. The ladder just overhangs a plastic rain gutter, which we can assume to be frictionless, so the force from the gutter on the ladder acts perpendicularly to the ladder. As a result, the top of the ladder experiences a normal force at an angle, while the bottom of the ladder experiences both a vertical normal force and a horizontal friction force. The center of mass of the ladder is 2 m from the bottom. The person is standing 3 m from the bottom. a.) What is the magnitude of the net force on the ladder at the top? Give your answer in newtons b.) What is the magnitude of the net force on the ladder at the bottom? Give your answer in newtonsarrow_forwardA lunch tray is being held in one hand, as the drawing illustrates. The mass of the tray itself is 0.300 kg, and its center of gravity is located at its geometrical center. On the tray is a 1.00 kg plate of food and a 0.330 kg cup of coffee. Obtain the force T exerted by the thumb and the force F exerted by the four fingers. Both forces act perpendicular to the tray, which is being held parallel to the ground.T = N (downward)F = N (upward)arrow_forwardA construction worker attempts to lift a uniform beam off the floor and raise it to a vertical position. The beam is 1.88 m long and weighs 490 N. At a certain instant the worker holds the beam momentarily at rest with one end a distance d = 1.02 m above the floor, as shown in the figure, by exerting a force P→ on the beam. (a) What is the magnitude of P→? (b) What is the magnitude of the (net) force of the floor on the beam? (c) What is the minimum value the coefficient of static friction between beam and floor can have in order for the beam not to slip at this instant?arrow_forward
- A uniform horizontal beam 5.00 m long and weighting 3.03 102 N is attached to a wall by a pin connection that allows the beam to rotate. Its far end is supported by a cable that makes an angle of 53.0° with the horizontal (Figure (a)). If a person weighing 6.05 102 N stands 1.60 m from the wall, find the magnitude of the tension in the cable and the force exerted by the wall on the beam. T = N Rx = N Ry = N Even if we selected some other axis for the torque equation, the solution would be the same. For example, if the axis were to pass through the center of gravity of the beam, the torque equation would involve both T and Ry. Together with Equations (1) and (2), however, the unknowns could still be found—a good exercise. In this example, notice the steps of the Problem-Solving Strategy could be carried out in the explicit recommended order.QUESTION What happens to the tension in the cable if the man in Figure (a) moves farther away from the wall? The tension would…arrow_forwardThe system shown in the diagram is in equilibrium. The object hanging from the end of the strut S weighs 513 kg and the strut itself weighs 107 kg. What is the horizontal component of the force exerted on the strut at point P? A) 797.67 N B) 12037. N C) 8681.8 N D) 7817.2 Narrow_forwardIn the figure, horizontal scaffold 2, with uniform mass m2 = 29 kg and length L2 = 2.3 m, hangs from horizontal scaffold 1, with uniform mass m1 = 54 kg. A 17 kg box of nails lies on scaffold 2, centered at distance d = 0.80 m from the left end. What is the tension T in the cable indicated?arrow_forward
- A 10 m ladder with a mass of 15 kg leans against the wall. If the ladder is in static equilibrium, what must be the normal force from the ground, assuming the wall is frictionless? 30 N 73.5 N 147 N 15 Narrow_forwardA ladder leans against a frictionless wall but is prevented from falling because of friction between it and the ground. Suppose you shift the base of the ladder toward the wall. Determine whether the following become larger, smaller, or stay the same (in magnitude): (a) the normal force on the ladder from the ground, (b) the force on the ladder from the wall, (c) the static frictional force on the ladder from the ground, and (d) the maximum value fs,max of the static frictional force.arrow_forwardA board with a weight of mg = 120.0 N and a length of 5.00 m is supported by two vertical ropes. Rope A is connected to one end of the board and rope B is connected at a distance d = 1.00 m from the other end of the board. A box with a weight Mg = 20.0 N is placed on the board with its center of mass at a distance d = 1.00 m from rope A. What are the tensions in the rope?arrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningCollege PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning