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All Textbook Solutions for Physics: Principles with Applications

82GP 83GP 84GP 85GP 86GP 87GP 88GP 89GP 90GP 91GP 92GP 93GP 94GP 1Q 2Q 3Q 4Q 5Q 6Q 7Q 8Q 9Q 10Q 11Q 12Q 13Q 14Q 15Q 16Q 17Q 18Q 19Q 1P 2P 3P 4P 5P 6P 7P 8P 9P 10P 11P 12P 13P 14P 15P 16P 17P 18P 19P 20P 21P 22P 23P 24P 25P 26P 27P 28P 29P 30P 31P 32P 33P 34P 35P 36P 37P 38P 39P 40P 41P 42P 43P 44P 45P 46P 47P 48P 49P 50P 51P 52P 53P 54P 55P 56P 57P 58P 59P 60P 61P 62GP 63GP 64GP 65GP 66GP 67GP 68GP 69GP 70GP 71GP 72GP 73GP 74GP 75GP 76GP 77GP 78GP 79GP 80GP 81GP A bicycle odometer (which counts revolutions and is calibrated to report distance traveled) is attached near the wheel axle and is calibrated for 27-inch wheels. What happens if you use it on a bicycle with 24-inch wheels?2Q 3Q Why is it more difficult to do a sit-up with your hands behind your head than when your arms are stretched out in front of you? A diagram may help you to answer this.If the net force on a system is zero, is the net torque also zero? If the net torque or a system is zero, is the net force zero? Explain and give examples.6Q 7Q Mammals that depend on being able to run fast have slender lower legs with flesh and muscle concentrated high, close to the body (Fig. 8-33). On the basis of rotational dynamics, explain why this distribution of mass is advantageous. Figure 8-33 This book has three symmetry axes through its center, all mutually perpendicular. The book’s moment of inertia would be smallest about which of the three? Explain.Can the mass of a rigid object be considered concentrated at its cm for rotational motion? Explain.The moment of inertia of a rotating solid disk about an axis through its cm is 12MR2(Fig. 8-20c). Suppose instead that a parallel axis of rotation passes through a point on the edge of the disk. Will the moment of inertia be the same, larger, or smaller? Explain why.Two inclines have the same height but make different angles with the horizontal. The same steel ball rolls without slipping down each incline. On which incline will the speed of the ball at the bottom be greater? Explain.Two spheres look identical and have the same mass. However, one is hollow and the other is solid. Describe an experiment to determine which is which.A sphere and a cylinder have the same radius and the same mass. They start from rest at the top of an incline. (a) Which reaches the bottom first? (b) Which has the greater speed at the bottom? (c) Which has the greater total kinetic energy at the bottom? (d) Which has the greater rotational kinetic energy? Explain your answers.15Q 16Q 17Q 15. Can the diver of Fig. 8-28 do a somersault without having any initial rotation when she leaves the board? Explain. 19Q When a motorcyclist leaves the ground on a jump and leaves the throttle on (so the rear wheel spins), why does the front of the cycle rise up?21Q 18. The angular velocity of a wheel rotating on a horizontal axle points west. In what direction is the linear velocity of a point on the top of the wheel? If the angular acceleration points east, describe the tangential linear acceleration of this point at the top of the wheel. Is the angular speed increasing or decreasing? 19. In what direction is the Earth's angular velocity vector as it rotates daily about its axis, north or south? 20. ‘On the basis of the law of conservation of angular momentum, discuss why a helicopter must have more than one rotor (or propeller). Discuss one or more ways the second propeller can operate in order to keep the helicopter stable. 1P 2P 3P 4P 5P 6P 7P 8P 9P 10P 11P 12P 13P 14P 15P 16P 17P 18P 19P 20P 21P 22P 23P 24P 25P 26P 27P 28P 29P 30P 31P 32P 33P 34P 35P 36P 37P 38P 39P 40P 41P 42P 43P 44P 45P 46P 47P 48P 49P 50P 51P 52P 53P 54P 55P 56P 57P 58P 59P 60P 61P 62P 63P 64P 65P 66P 67P 68GP 69GP 70GP 71GP 72GP 73GP 74GP 75GP 76GP 77GP 78GP 79GP 80GP 81GP 82GP 83GP 84GP 85GP 86GP Describe several situations in which an object is not in equilibrium even though the net force on it is zero 2Q You can find the center of gravity of a meter stick by resting it horizontally on your two index fingers, and then slowly drawing your fingers together. First the meter stick will slip on one finger, and then on the other, but eventually the fingers meet at the cg.Why does this work?4Q A ground retaining wall is shown in Fig. 9-36a .The ground, particularly when wet, can exert a significant force F on the wall, (a) What force produces the torque to keep the wall upright? (b)Explain why the retaining wall in Fig. 9-36bwould be much less likely to overturn than that in Fig. 9-36a Can the sum of the torques on an object be zero while the net force on the object is nonzero? Explain A ladder, leaning against a wall, makes a 60° angle with the ground. When is it more likely to slip: when a person stands on the ladder near the top or near the bottom? Explain.A uniform meter stick supported at the 25-cm mark is in equilibrium when a 1 -kg rock is suspended at the 0-cm end (as shown in Fig. 9-37).Is the mass of the meter stick greater than, equal to, or less than the mass of the rock? Explain your reasoning,Why do you tend to lean backward when carrying a heavy load in your arms?Figure 9-38 shows a cone. Explain how to lay it on a flat table so that it is in (a) stable equilibrium, (b) unstable equilibrium, (c) neutral equilibrium.11Q Why is it not possible to sit upright in a chair and rise to your feet without first leaning forward?Why is it more difficult to do sit-ups when your knees are bent than when your legs are stretched out?Explain why touching your toes while you are seated on the floor with outstretched legs produces less stress on the lower spinal column than when touching your toes from a standing position. Use a diagram.15Q Name the type of equilibrium for each position of the ball in ball in figure 9-40 A Figure 9-40 ( 17. ) Is the Young's modulus for a bungee cord smaller or larger than that for an ordinary rope? 18Q 19Q Three forces are applied to a tree sapling, as shown in Fig.9-46, to stabilize it. If FA=385N and FB=475 N, fing FCin magnitude and direction.2P 3(I) A tower crane ( Fig. 9-48a) must always be carefully balanced so that there is no net torque tending to tip it. A particular crane at a building site is about to lift a 2800-kg air-conditioning unit. The crane’s dimensions are shown in Fig. 9-48b. (a) Where must the crane’s 9500-kg counterweight be placed when the load is lifted from the ground? (The counterweight is usually moved automatically via sensors and motors to precisely compensate for the load) (b) Determine the maximum load that can be lifted with this counterweight when it is placed at its full extent. Ignore the mass of the beam. What is the mass of the diver in Fig. 9-49 if she exerts a torque of 1800m. N on the board, relative the left (A) support post?5P 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 Ft = Ff= 11 0 N, what force do the forceps jaws exert on the plastic rod? Figure 9-50 7P The two trees in Fig. 9-51 are 6.6 m apart. A backpacker 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 9P 10P 11P Find the tension in the two cords shown in Fig. 9-52. Neglect the mass of the cords, and assume that the angle is 330and the mass m is 190 kg.13P 14P The force required to pull the cork out of the top of a wine bottle is in the range of 200 to 400 N.What range of forces F is required to open a wine bottle with the bottle opener shown in Fig. 9-55? Figure 9-55 16P Three children are trying to balance on a seesaw, which includes a fulcrum rock acting as a pivot at the center, and a very light board 3.2 m long (Fig. 9-57).Two playmates are already on either end. Boy A has a mass of 45 kg, and boy B a mass of 35 kg. Where should girl C, whose mass is 25 kg, place herself so as to balance the seesaw? Figure 9-57 A shop sign weighing 215 N hangs from the end of a uniform 155-N beam as shown in Fig. 9-58. Find the tension in the supporting wire (at 35.00)and the horizontal and vertical forces exerted by the hinge on the beam at the wall.[ Hint. First draw a free-body diagram.]19P 20P 21P 22 (II) A 20.0-m-long uniform beam weighing 650 N rests on walls A and B, as shown in Fig. 9-62 (a) Find the maximum weight of a person who can walk to the extreme end D without tipping the beam Find the forces that the walls A and B exert on the beam when the person is standing: (b) at D: (c) 2.0 m to the right of A. - - Figure 9-62 23P 24P 25P 26P A uniform rod AB of length 5.0 m and mass M=3.S kg is hinged at A and held in equilibrium by a light cord, as shown in Fig. 9-57.A load W=22N hangs from the rod at a distance d so that the tension in the cord is 85 N. (a) Draw a free-body diagram for the rod. (b) Determine the vertical and horizontal forces on the rod exerted by the hinge, (c) Determine d from the appropriate torque equation.You are on a pirate ship and being forced to walk the plank (Fig. 9-68) You are standing at the point marked C. The plank is nailed onto the deck at point A, and rests on the support 0.75 m away from A The center of mass of the uniform plank is located at point B. Your mass is 65 kg and the mass of the plank is 45 kg. What is the minimum downward force the nails must exert on the plank to hold it in place? Figure 9-68 29P 30P 31P 32P 33P 34P 35P If 25 kg is the maximum mass m that a person can hold in a hand when the arm is positioned with a 105 angle at the elbow as shown in Fig. 9-74, what is the maximum force Fmax that the biceps muscle exerts on the forearm ? Assume the forearm and hand have a total mass of 2.0 kg with a CG that is 15 cm from the elbow, and that the biceps muscle attaches 5.0 cm from the elbow.37P 38P 39P A marble column of cross-sectional area 1.4 m2 supports a mass of 25,000 kg. (a) Whais the stress within the column? (b) What is the strain?41P A sign (mass 1700 kg) hangs from the bottom end of a vertical steel girder with a cross-sectional area of 0.012 m2. (a) What is the stress within the girder? (b) What is the strain on the girder? (c) If the girder is 9.50 m long,how much is it lengthened? (Ignore the mass of the girder itself.)43P 44P 45P A steel wire 2.3 mm in diameter stretches by 0.030% when a mass is suspended from it. How large is the mass?47P 48P 49P 50P 51P (a) What is the minimum cross-sectional area required of a vertical steel cable from which is suspended a 270-kg chandelier? Assume a safety factor of 7.0. (b) If the cable is 7.5 m long, how much does it elongate?53P 54P 55P 56P 57GP 58GP

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