(II) The two trees in Fig. 9–51 are 6.6 m apart. A back- packer is trying to lift his pack out of the reach of bears. Calculate the magnitude of the force F that he must exert downward to hold a 19-kg backpack so that the rope sags at its midpoint by (a) 1.5 m, (b) 0.15 m. FIGURE 9–51 Problems 8 and 70.

(II) The two trees in Fig. 9–51 are 6.6 m apart. A back- packer is trying to lift his pack out of the reach of bears. Calculate the magnitude of the force F that he must exert downward to hold a 19-kg backpack so that the rope sags at its midpoint by (a) 1.5 m, (b) 0.15 m. FIGURE 9–51 Problems 8 and 70.

College Physics

11th Edition

ISBN:9781305952300

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter1: Units, Trigonometry. And Vectors

Section: Chapter Questions

Problem 1CQ: Estimate the order of magnitude of the length, in meters, of each of the following; (a) a mouse, (b)...

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(II) A man doing push-ups pauses in the position shown in Fig. 9–65. His mass m = 68 kg. Determine the normal force exerted by the floor (a) on each hand; (b) on each foot. 28 cm mg 42 cm 95 cm FIGURE 9-65 Problem 25.
A 23.0-kg backpack is suspended midway between two trees by a light cord as in Fig. 9–51. A bear grabs the backpack and pulls vertically downward with a constant force, so that each section of cord makes an angle of 27° belowthe horizontal. Initially, without the bear pulling, the angle was 15°; the tension in the cord with the bear pulling is double what it was when he was not. Calculate the force the bear is exerting on the backpack.
In a mountain-climbing technique called the "Tyrolean tra- verse," a rope is anchored on both ends (to rocks or strong trees) across a deep chasm, and then a climber traverses the rope while attached by a sling as in Fig. 9–91. This technique generates tremendous forces in the rope and anchors, so a basic understanding of physics is crucial for safety. A typical climbing rope can undergo a tension force of perhaps 29 kN before breaking, and a “safety factor" of 10 is usually recom- mended. The length of rope used in the Tyrolean traverse must allow for some “sag" to remain in the recommended safety range. Consider a 75-kg climber at the center of a Tyrolean traverse, spanning a 25-m chasm. (a) To be within its recommended safety range, what minimum distance x must the rope sag? (b) If the Tyrolean traverse is set up incorrectly so that the rope sags by only one-fourth the distance found in (a), determine the tension in the rope. Ignore stretching of the rope. Will the rope break? 25 m…
(II) Find the tension in the two wires supporting the traffic light shown in Fig. 9–53. 53° 37 O 33 kg FIGURE 9–53 Problem 13.
(II) A 0.75-kg sheet is centered on a clothesline as shown in Fig. 9-63. The clothesline on either side of the hanging sheet makes an angle of 3.5° with the horizontal. Calculate the tension in the clothesline (ignore its mass) on either side of the sheet. Why is the tension so much greater than the weight of the sheet? 3.5° 3.5° FIGURE 9-63 Problem 23.
(II) Two cords support a chandelier in the manner shownin Fig. 9–4 except that the upper cord makes an angle of45° with the ceiling. If the cords can sustain a force of1660 N without breaking, what is the maximum chandelierweight that can be supported?
(II) A 2500-kg trailer is attached to a stationary truck at point B, Fig. 9–61. Determine the normal force exerted by the road on the rear tires at A, and the vertical force exerted on the trailer by the support B. B Mg 2.5 m 5.5 m FIGURE 9-61 Problem 21.
The two planks in Fig. 6–30a are connected together by cable BC anda smooth spacer DE. Draw the free-body diagram of the system of both planks andapply MA = 0 to determine NF. Then use the free-body diagram ofCEF to determine FDE and FBC.
A 25-kg object is being lifted by two people pulling on the ends of a 1.15-mm-diameter nylon cord that goes over two 3.00-m-high poles 4.0 m apart, as shown in Fig. 9–86. How high above the floor will the object be when the cord breaks? 25 kg FIGURE 9-86 Problem 69.
(II) A (lightweight) pallet has a load of ten identical cases of tomato paste (see Fig. 7–39), each of which is a cube of length l. Find the center of gravity in the horizontal plane, so that the crane operator can pick up the load without tip- ping it. FIGURE 7-39 Problem 53.
(II) Figure 9–50 shows a pair of forceps used to hold a thin plastic rod firmly. If the thumb and finger each squeeze with a force Fr = FF = 11.0 N, what force do the forceps jaws exert on the plastic rod? Jaws Rod Fr P FIGURE 9-50 8.50 cm 2.70 cm Problem 6.
A 2.0-m-high box with a 1.0-m-square base is moved across a rough floor as in Fig. 9–89. The uniform box weighs 250N and has a coefficient of static friction with the floor of 0.60. What minimum force must be 1.0 m exerted on the box to make it slide? What is the maximum height h above the floor that this force can be applied without tip- ping the box over? Note that as the box tips, the normal force CG 2.0 m FN and the friction force will act at the lowest corner. Fir FIGURE 9-89 Problem 74.