College Physics: A Strategic Approach (4th Edition)
4th Edition
ISBN: 9780134609034
Author: Randall D. Knight (Professor Emeritus), Brian Jones, Stuart Field
Publisher: PEARSON
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Chapter 7, Problem 26MCQ
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A. Who should sit farther from the center of a uniform seesaw, a 93-kg man or his 33-kg son, for the seesaw to remain in a horizontal position? Explain. B. Illustrate the figure and solve the problem by showing complete solution. Ella weighing 225 N sits at one end of a see-saw 4 m long. If Omar sits opposite her 150 cm away from the center, they balance each other. What is the weight of Omar? ( Disregard the weight of the seesaw)
An athlete at the gym holds a 3.0 kg steel ball in his hand. His arm is 70 cm long and has a mass of 3.8 kg, with the center of mass at 40% of the arm length from the shoulder.
a. What is the magnitude of the torque about his shoulder due to the weight of the ball and his arm if he holds his arm straight out to his side, parallel to the floor?
b. What is the magnitude of the torque about his shoulder due to the weight of the ball and his arm if he holds his arm straight, but 45∘ below horizontal?
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a. If m1 = 12 g and m2 = 10 g, find the value of m3 in order for this mobile to sit in equilibrium.
b. If the torque exerted by the tension on the cable is 1300 Nm, what must be the mass of the beam?
Chapter 7 Solutions
College Physics: A Strategic Approach (4th Edition)
Ch. 7 - The batter in a baseball game hits a home run. As...Ch. 7 - Viewed from somewhere in space above the north...Ch. 7 - Figure Q7.3 shows four pulleys, each with a heavy...Ch. 7 - If you are using a wrench to loosen a very...Ch. 7 - Prob. 5CQCh. 7 - Prob. 6CQCh. 7 - Prob. 7CQCh. 7 - A screwdriver with a very thick handle requires...Ch. 7 - If you have ever driven a truck, you likely found...Ch. 7 - A student gives a steady push to a ball at the end...
Ch. 7 - Prob. 11CQCh. 7 - If you grasp a hammer by its lightweight handle...Ch. 7 - Prob. 13CQCh. 7 - Prob. 15CQCh. 7 - The moment of inertia of a uniform rod about an...Ch. 7 - Prob. 17CQCh. 7 - With care, its possible to walk on top of a barrel...Ch. 7 - A nut needs to be tightened with a wrench. Which...Ch. 7 - Prob. 20MCQCh. 7 - Prob. 21MCQCh. 7 - Prob. 22MCQCh. 7 - Prob. 23MCQCh. 7 - A typical compact disk has a mass of 15 g and a...Ch. 7 - Two horizontal rods are each held up by vertical...Ch. 7 - Prob. 26MCQCh. 7 - Questions 25 through 27 concern a classic...Ch. 7 - Questions 25 through 27 concern a classic...Ch. 7 - Questions 25 through 27 concern a classic...Ch. 7 - What is the angular position in radians of the...Ch. 7 - A child on a merry-go-round takes 3.0 s to go...Ch. 7 - What is the angular speed of the tip of the minute...Ch. 7 - An old-fashioned vinyl record rotates on a...Ch. 7 - The earths radius is about 4000 miles. Kampala,...Ch. 7 - Prob. 6PCh. 7 - A turntable rotates counterclockwise at 78 rpm. A...Ch. 7 - Prob. 8PCh. 7 - Prob. 9PCh. 7 - Prob. 10PCh. 7 - The 1.00-cm-long second hand on a watch rotates...Ch. 7 - The earths radius is 6.37 106 m; it rotates once...Ch. 7 - To throw a discus, the thrower holds it with a...Ch. 7 - Prob. 14PCh. 7 - A computer hard disk starts from rest, then speeds...Ch. 7 - Prob. 16PCh. 7 - The crankshaft in a race car goes from rest to...Ch. 7 - Reconsider the situation in Example 7.10. If Luis...Ch. 7 - Prob. 19PCh. 7 - Prob. 20PCh. 7 - What is the net torque about the axle on the...Ch. 7 - The tune-up specifications of a car call for the...Ch. 7 - In Figure P7.22, force F2, acts half as far from...Ch. 7 - A professors office door is 0.91 m wide, 2.0 m...Ch. 7 - What is the net torque on the bar shown in Figure...Ch. 7 - Prob. 26PCh. 7 - Prob. 27PCh. 7 - Prob. 28PCh. 7 - What is the net torque on the bar shown in Figure...Ch. 7 - Prob. 30PCh. 7 - The 2.0 kg, uniform, horizontal rod in Figure...Ch. 7 - A 4.00-m-long, 500 kg steel beam extends...Ch. 7 - An athlete at the gym holds a 3.0 kg steel ball in...Ch. 7 - The 2.0-m-long, 15 kg beam in Figure P7.34 is...Ch. 7 - Prob. 35PCh. 7 - Hold your arm outstretched so that it is...Ch. 7 - Prob. 37PCh. 7 - Prob. 38PCh. 7 - A regulation table tennis ball is a thin spherical...Ch. 7 - Prob. 40PCh. 7 - A solid cylinder with a radius of 4.0 cm has the...Ch. 7 - Prob. 42PCh. 7 - A bicycle rim has a diameter of 0.65 m and a...Ch. 7 - Prob. 44PCh. 7 - A small grinding wheel has a moment of inertia of...Ch. 7 - Prob. 46PCh. 7 - An objects moment of inertia is 2.0 kg m2. Its...Ch. 7 - Prob. 48PCh. 7 - A 200 g, 20-cm-diameter plastic disk is spun on an...Ch. 7 - Prob. 50PCh. 7 - A frictionless pulley, which can be modeled as a...Ch. 7 - Prob. 52PCh. 7 - If you lift the front wheel of a poorly maintained...Ch. 7 - Prob. 54PCh. 7 - A toy top with a spool of diameter 5.0 cm has a...Ch. 7 - Prob. 56PCh. 7 - A bicycle with 0.80-m-diameter tires is coasting...Ch. 7 - Prob. 58PCh. 7 - Prob. 59PCh. 7 - Prob. 60PCh. 7 - Prob. 61GPCh. 7 - The grap in Figure P7.56 shows the angular...Ch. 7 - A car with 58-cm-diameter tires accelerates...Ch. 7 - The cable lifting an elevator is wrapped around a...Ch. 7 - The 20-cm-diameter disk in Figure P7.59 can rotate...Ch. 7 - A combination lock has a 1.0-cm-diameter knob that...Ch. 7 - A 70 kg mans arm, including the hand, can be...Ch. 7 - Prob. 68GPCh. 7 - A reasonable estimate of the moment of inertia of...Ch. 7 - Prob. 70GPCh. 7 - The ropes in Figure P7.65 are each wrapped around...Ch. 7 - Flywheels are large, massive wheels used to store...Ch. 7 - A 1.0 kg ball and a 2.0 kg ball are connected by a...Ch. 7 - Prob. 76GPCh. 7 - A tradesman sharpens a knife by pushing it with a...Ch. 7 - MCAT-Style Passage Problems The Bunchberry The...Ch. 7 - The Bunchberry The bunchberry flower has the...Ch. 7 - The Bunchberry The bunchberry flower has the...Ch. 7 - Prob. 81MSPPCh. 7 - Prob. 82MSPPCh. 7 - Prob. 83MSPPCh. 7 - Prob. 84MSPP
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- (a) When opening a door, you push on it perpendicularly with a force of 55.0 N at a distance of 0.850m from the hinges. What torque are you exerting relative to the hinges? (b) Does it matter if you push at the same height as the hinges?arrow_forwardA 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_forwardTorque and the Two Conditions for Equilibrium 17. The arm in Figure P8.17 weighs 41.5 N. The force of gravity acting on the arm acts through point A. Determine the magnitudes of the tension force Ft, in the deltoid muscle and the force Fs exerted by the shoulder on the humerus (upper-arm bone) to hold the arm in the position shown. Figure P8.17arrow_forward
- a.)A mother is helping her children, of unequal weight, to balance on a seesaw so that they will be able to make it tilt back and forth without the heavier child simply sinking to the ground. Given that her heavier child of weight W is sitting a distance L to the left of the pivot, at what distance L1 must she place her second child of weight w on the right side of the pivot to balance the seesaw? Express your answer in terms of L, W, and w.arrow_forwardA uniform, 267 N rod that is 2.06 mm long carries a 225 N weight at its right end and an unknown weight WW toward the left end (see the figure below). When WW is placed 55.9 cm from the left end of the rod, the system just balances horizontally when the fulcrum is located 74.7 cm from the right end. a. What is w (in N)? b. If the weight w is moved 25.3 cm to the right, how far must the fulcrum (balance point) be moved to restore balance? 225 N Figure 1. A mass rests on the left side of a balance beam.arrow_forwardA meter stick balances horizontally on a knife-edge at the 50.0 cm mark. With two 3.89 g coins stacked over the 31.9 cm mark, the stick is found to balance at the 40.9 cm mark. What is the mass of the meter stick? Number i Units garrow_forward
- Three children are trying to balance on a seesaw, which consists of a fulcrum rock, acting as a pivot at the center, and a very light board 3.4 m long (Figure 1). Two playmates are already on either end. Boy A has a mass of 45 kg, and boy B a mass of 35 kg. ▼ Part A Where should girl C, whose mass is 25 kg, place herself so as to balance the seesaw? Express your answer to two significant figures and include the appropriate units. for Part A for Part Addo for Part redo for Part A reset for Part A keyboard shortcuts for Part A help for Part A x= Value Unitsarrow_forwarda. A downward force with magnitude 3N is applied to the right end of the rod. What is the torque on the rod about an axis through the pivot point (on the left end)? Give magnitude and direction. b. An upward force with magnitude 6N is applied to the middle of the rod. What is the torque on the rod about an axis through the pivot point (on the left end)? Give magnitude and direction. c. If both forces described in parts a and b are applied at the same time, what is the net torque on the rod?arrow_forwardItem 6 A 4.80-m-long, 500 kg steel uniform beam extends horizontally from the point where it has been bolted to the framework of a new building under construction. A 70 kg construction worker stands at the far end of the beam. Part A What is the magnitude of the torque about the bolt due to the worker and the weight of the beam? T = VE ΑΣΦ ? N.marrow_forward
- 3. A meter stick has a pivot that is located in the middle (50 cm). On this meter stick we place 150 g @ 32 cm, 300 g @ 45 cm, 100 g @80 cm and 300 g @80 cm. a. How much mass needs to be placed at 55 cm in order to balance the meter stick. b. Where will you put 500 g in order to balance the meter stick?arrow_forwardKatherine is attempting a biceps curl with a 100 N dumbbell. She is standing upright, and her forearm is horizontal. The moment arm of the dumbbell about Katherine’s elbow joint is 30 cm.a. What torque is created by the dumbbell about the elbow joint?b. If the elbow flexor muscles contract with a force of 1000 N and hold the barbell in static equilibrium, what is the moment arm of the elbow flexor muscles about the elbow joint?arrow_forwardA uniform, 255-N rod that is 2 m long carries a 225-N weight at its right end and an unknown weight toward the left end. When W is placed 50 cm from the left end of the rod, the system just balance horizontally when the fulcrum is located 75 cm from the right end.a. Find W.b. If W is now moved 25 cm to the right, how far and in what direction must the fulcrum be moved to restore balance?arrow_forward
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