Conceptual Physics / MasteringPhysics (Book & Access Card)
12th Edition
ISBN: 9780321908605
Author: Paul G. Hewitt
Publisher: PEARSON
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Textbook Question
Chapter 7, Problem 56RCQ
Why do you do no work on a 25-kg backpack when you walk a horizontal distance of 100 m?
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Chapter 7 Solutions
Conceptual Physics / MasteringPhysics (Book & Access Card)
Ch. 7 - When is energy most evident?Ch. 7 - A force sets an object in motion. When the force...Ch. 7 - Cite an example in which a force is exerted on an...Ch. 7 - Prob. 4RCQCh. 7 - Exactly what is it that enables an object to do...Ch. 7 - If both sacks in the preceding question are lifted...Ch. 7 - A car is raised a certain distance in a...Ch. 7 - Two cars are raised to the same elevation on...Ch. 7 - When is the potential energy of something...Ch. 7 - Prob. 10RCQ
Ch. 7 - 11. Compared with a car moving at some original...Ch. 7 - If you push a crate horizontally with 100 N across...Ch. 7 - 13. How does speed affect the friction between a...Ch. 7 - 14. What will be the kinetic energy of a pile...Ch. 7 - An apple hanging from a limb has potential energy...Ch. 7 - 16. What is the source of energy in sunshine?
Ch. 7 - Prob. 17RCQCh. 7 - 18. Can a machine multiply input force? Input...Ch. 7 - 19. If a machine multiplies force by a factor of...Ch. 7 - 20. A force of 50 N is applied to the end of a...Ch. 7 - 21. What is the efficiency of a machine that...Ch. 7 - Prob. 22RCQCh. 7 - Prob. 23RCQCh. 7 - Prob. 24RCQCh. 7 - 25. Can we correctly say that hydrogen is a new...Ch. 7 - Prob. 26RCQCh. 7 - Prob. 27RCQCh. 7 - Prob. 28RCQCh. 7 - Prob. 29RCQCh. 7 - Prob. 30RCQCh. 7 - Prob. 31RCQCh. 7 - Power = work/time: P = W / t 32. Show that 50 W of...Ch. 7 -
33. Show that about 786 W of power is expended...Ch. 7 - Prob. 34RCQCh. 7 - 35. Show that the gravitational potential energy...Ch. 7 - Kinetic energy= 1 2 mass X speed : KE= 1 2 m v 2...Ch. 7 - 37. Calculate the kinetic energy of an 84-kg...Ch. 7 - Work-energy theorem: Work = KE
38. Show...Ch. 7 - 39. Show that a 2,500,000-J change in kinetic...Ch. 7 - Prob. 40RCQCh. 7 - Prob. 41RCQCh. 7 - 42. (a) How much work is done when you push a...Ch. 7 - 43. This question is typical on some driver’s...Ch. 7 - Belly-flop Bernie dives from atop a tall flagpole...Ch. 7 - Nellie Newton applies a force of 50 N to the end...Ch. 7 - 46. Consider an ideal pulley system. If you pull...Ch. 7 - 47. In raising a 5000-N piano with a pulley...Ch. 7 - 48. In the hydraulic machine shown, you observe...Ch. 7 - 49. How many watts of power do you expend when you...Ch. 7 - Emily holds a banana of mass m over the edge of a...Ch. 7 - 51. The mass and speed of the three vehicles, A,...Ch. 7 - 52. A ball is released from rest at the left of...Ch. 7 - 53. The roller coaster ride starts from rest at...Ch. 7 - Prob. 54RCQCh. 7 - Prob. 55RCQCh. 7 - Why do you do no work on a 25-kg backpack when you...Ch. 7 - If your friend pushes a lawnmower four times as...Ch. 7 - Why does one get tired pushing against a...Ch. 7 - Prob. 59RCQCh. 7 - Prob. 60RCQCh. 7 - Prob. 61RCQCh. 7 - When a rifle with a longer barrel is fired, the...Ch. 7 - Prob. 63RCQCh. 7 - 64. You and a flight attendant toss a ball back...Ch. 7 - Prob. 65RCQCh. 7 - Prob. 66RCQCh. 7 - Prob. 67RCQCh. 7 - Prob. 68RCQCh. 7 - 69. A physics instructor demonstrates energy...Ch. 7 - Prob. 70RCQCh. 7 - Prob. 71RCQCh. 7 - 72. A moving hammer hits a nail and drives it into...Ch. 7 - Prob. 73RCQCh. 7 - 74. Why does the force of gravity do work on a car...Ch. 7 - Prob. 75RCQCh. 7 - Prob. 76RCQCh. 7 - Prob. 77RCQCh. 7 - Prob. 78RCQCh. 7 - Prob. 79RCQCh. 7 - Prob. 80RCQCh. 7 - Prob. 81RCQCh. 7 - Prob. 82RCQCh. 7 - Prob. 83RCQCh. 7 - Prob. 84RCQCh. 7 - Prob. 85RCQCh. 7 - When the velocity of an object is doubled, by what...Ch. 7 - Prob. 87RCQCh. 7 - Prob. 88RCQCh. 7 - Prob. 89RCQCh. 7 - If your momentum is zero, is your kinetic energy...Ch. 7 - 91. If two objects have equal kinetic energies, do...Ch. 7 - 92. Two lumps of clay with equal and opposite...Ch. 7 - Scissors for cutting paper have long blades and...Ch. 7 - Prob. 94RCQCh. 7 - Prob. 95RCQCh. 7 - Prob. 96RCQCh. 7 - Prob. 97RCQCh. 7 - Prob. 98RCQCh. 7 - Prob. 99RCQCh. 7 - 100. Consider the identical balls released from...Ch. 7 - Prob. 101RCQCh. 7 - Prob. 102RCQCh. 7 - Prob. 103RCQCh. 7 - Prob. 104RCQCh. 7 - Prob. 105RCQCh. 7 - Prob. 106RCQCh. 7 - Prob. 107RCQCh. 7 - Prob. 108RCQCh. 7 - 109. Your discussion partner is confused about...Ch. 7 - 110. In the absence of air resistance, a ball...Ch. 7 - 111. You’re on a rooftop and you throw one ball...Ch. 7 - 112. In the pulley system shown, block A has a...Ch. 7 - Prob. 113RCQCh. 7 - Prob. 114RCQCh. 7 - Prob. 115RCQCh. 7 - Prob. 116RCQCh. 7 - Prob. 117RCQCh. 7 - 118. Consider a bob attached by a string, a simple...Ch. 7 - Consider a satellite in a circular orbit above...Ch. 7 - 120. Consider the swinging-balls apparatus. If two...Ch. 7 - To combat wasteful habits, we often speak of...Ch. 7 - Prob. 122RCQ
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- Two students throw identical snowballs from the same height; both snowballs having the same initial speed vo ( Fig. 4.25). Which snowball has the greater speed on striking the level ground at the bottom of the slope? Justify your answer using energy considerations. Figure 4.25 Away They Go! See Short Answer Question 16.arrow_forwardA mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance?arrow_forwardCite two examples in which a force is exerted on an object without doing any work on the object.arrow_forward
- Suppose you are jogging at constant velocity. Are you doing any work on the environment and vice versa?arrow_forwardWhat average power is generated by a 70.0-kg moun-tain climber who climbs a summit of height 325 in in 95.0 min? (a) 39.1 W (b) 54.6 W (c) 25.5 W (d) 67.0 W (e) 88.4 Warrow_forwardA sled of mass 70 kg starts from rest and slides down a 10 incline 80 m long. It then travels for 20 m horizontally before starting back up an 8° incline. It travels 80 m along this incline before coming to rest. What is the magnitude of the net work done on the sled by friction?arrow_forward
- What is the dominant factor that affects the speed of an object that started from rest down a frictionless incline if the only work done on the object is from gravitational forces?arrow_forwardA 0.20-kg ball is thrown upward. How much work is done on the ball by gravity as the ball rises between heights of 2.0 m and 3.0 m?arrow_forwardHow much work is done by the boy pulling his sister 30.0 m in a wagon as shown in Figure 7.36? Assume no friction acts on the wagon. Figure 7.36 The boy does work on the system of the wagon and the child when he pulls them as shown.arrow_forward
- In the movie Monty Python and the Holy Grail (https://openstaxcollege. org/l/21monpytmovcl) a cow is catapulted from the top of a castle wall over to the people down below. The gravitational potential energy is set to zero at ground level. The cow is launched from a spring of spring constant 1.1 104 N/m that is expanded 0.5 m from equilibrium. If the castle is 9.1 m tall and the mass of the cow is 110 kg, (a) what is the gravitational potential energy of the cow at the top of the castle? (b) What is the elastic spring energy of the cow before the catapult is released? (c) What is the speed of the cow right before it lands on the ground?arrow_forwardThe swimmer shown in Figure 7.44 exerts an average horizontal backward force of 80.0 N with his arm during each 1.80 m long stroke. (a) What is his work output in each stroke? (b) Calculate the power output of his arms if he does 120 strokes per minute. Figure 7.44arrow_forwardThe force acting on a particle varies as shown in Figure P6.14. Find the work done by the force on the particle as it moves (a) from x = 0 to x = 8.00 m, (b) from x = 8.00 m to x= 10.0 m, and (c) from x = 0 to x = 10.0 m.arrow_forward
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Mechanical work done (GCSE Physics); Author: Dr de Bruin's Classroom;https://www.youtube.com/watch?v=OapgRhYDMvw;License: Standard YouTube License, CC-BY