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Your brother is opening a skateboard shop. He has created a sign for his shop made from a uniform material and in the shape shown in Figure P12.5. The shape of the sign represents one of the hills in the skateboard park he plans on building on land adjacent to the shop. The curve on the top of the sign is described by the function y = (x − 3)2/9. When the sign arrives in his shop, your brother wants to hang it from a single wire outside the shop. But he doesn’t know where on the sign to attach the wire so that the bottom edge of the sign will hang in a horizontal orientation. He asks for your help.
Figure P12.5
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Chapter 12 Solutions
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- Your brother is opening a skateboard shop. He has created a sign for his shop made from a uniform material and in the shape shown in Figure P12.5. The shape of the sign represents one of the hills in the skateboard park he plans on building on land adjacent to the shop. The curve on the top of the sign is described by the function y = (x 3)2/9. When the sign arrives in his shop, your brother wants to hang it from a single wire outside the shop. But he doesnt know where on the sign to attach the wire so that the bottom edge of the sign will hang in a horizontal orientation. He asks for your help. Figure P12.5arrow_forwardThree forces are exerted on the disk shown in Figure P12.71,and their magnitudes are F3 = 2F2 = 2F1. The disks outer rimhas radius R, and the inner rim has radius R/2. As shown in thefigure, F1 and F3 are tangent to the outer rim of the disk, and F2 is tangent to the inner rim. F3 is parallel to the x axis, F2 is parallel to the y axis, and F1 makes a 45 angle with the negative x axis. Find expressions for the magnitude of each torque exertedaround the center of the disk in terms of R and F1. FIGURE P12.71 Problems 71-75arrow_forwardFigure P12.38 shows a light truss formed from three struts lying in a plane and joined by three smooth hinge pins at their ends. The truss supports a downward force of F=1000N applied at the point B. The truss has negligible weight. The piers at A and C are smooth. (a) Given 1 = 30.0 and 2 = 45.0, find nA and nC. (b) One can show that the force any strut exerts on a pin must be directed along the length of the strut as a force of tension or compression. Use that fact to identify the directions of the forces that the struts exert on the pins joining them. Find the force of tension or of compression in each of the three bars. Figure P12.38arrow_forward
- A stepladder of negligible weight is constructed as shown in Figure P12.40, with AC = BC = . A painter of mass m stands on the ladder a distance d from the bottom. Assuming the floor is frictionless, find (a) the tension in the horizontal bar DE connecting the two halves of the ladder, (b) the normal forces at A and B, and (c) the components of the reaction force at the single hinge C that the left half of the ladder exerts on the right half. Suggestion: Treat the ladder as a single object, but also treat each half of the ladder separately. Figure P12.40 Problems 40 and 41.arrow_forwardReview. One end of a light spring with force constant k = 100 N/m is attached to a vertical wall. A light string is tied to the other end of the horizontal spring. As shown in Figure P12.57, the string changes from horizontal to vertical as it passes over a pulley of mass M in the shape of a solid disk of radius R = 2.00 cm. The pulley is free to turn on a fixed, smooth axle. The vertical section of the string supports an object of mass m = 200 g. The string does not slip at its contact with the pulley. The object is pulled downward a small distance and released. (a) What is the angular frequency of oscillation of the object in terms of the mass M? (b) What is the highest possible value of the angular frequency of oscillation of the object? (c) What is the highest possible value of the angular frequency of oscillation of the object if the pulley radius is doubled to R = 4.00 cm? Figure P12.57arrow_forwardWhile working on homework together, your friend stands her pencil on its sharpened tip. You say, Nice trick. How did you do it? Why do you think some trick had to be involved? Would you ask the same question if the pencil were lying on its side or if the pencil were unsharpened?arrow_forward
- A 10 000-N shark is supported by a rope attached to a 4.00-m rod that can pivot at the base. (a) Calculate the tension in the cable between the rod and the wall, assuming the cable is holding the system in the position shown in Figure P12.33. Find (b) the horizontal force and (c) the vertical force exerted on the base of the rod. Ignore the weight of the rod. Figure P12.33arrow_forwardTwo racquetballs, each having a mass of 170 g, are placed in a glass jar as shown in Figure P12.43. Their centers lie on a straight line that makes a 45 angle with the horizontal. (a) Assume the walls are frictionless and determine P1, P2, and P3. (b) Determine the magnitude of the force exerted by the left ball on the right ball. Figure P12.43arrow_forwardConsider a nanotube with a Youngs modulus of 2.130 1012 N/m2 that experiences a tensile stress of 5.3 1010 N/m2. Steel has a Youngs modulus of about 2.000 1011 Pa. How much stress would cause a piece of steel to experience the same strain as the nanotube?arrow_forward
- During a visit to New York City, Lil decides to estimate the height of the Empire State Building (Fig. P1.57). She measures the angle of elevation of the spire atop the building as 20. After walking 9.0 102 ft closer to the iconic building, she finds the angle to be 25. Use Lils data to estimate the height h of the Empire State Building.arrow_forwardA 50.0−kg woman wearing high-heeled shoes is invited into a home in which the kitchen has vinyl floor covering. The heel on each show is circular and has a radius of 0.500 cm. Should the homeowner be concerned? Explain your answer.arrow_forward
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