Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)
4th Edition
ISBN: 9780133942651
Author: Randall D. Knight (Professor Emeritus)
Publisher: PEARSON
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Chapter 9, Problem 8CQ
8. You need to raise a heavy block by pulling it with a massless rope. You can either (a) pull the block straight up height h, or (b) pull it up a long, frictionless plane inclined at a 15° angle until its height has increased by h. Assume you will move the block at constant speed either way. Will you do more work in case a or case b? Or is the work the same in both cases? Explain.
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Chapter 9 Solutions
Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)
Ch. 9 - If a particle’s speed increases by a factor of 3,...Ch. 9 - Prob. 2CQCh. 9 - 3. An elevator held by a single cable is ascending...Ch. 9 - The rope in FIGURE Q9.4 pulls the box to the left...Ch. 9 - 5. A 0.2 kg plastic cart and a 20 kg lead cart...Ch. 9 - A particle moving to the left is slowed by a force...Ch. 9 - 7. A particle moves in a vertical plane along the...Ch. 9 - 8. You need to raise a heavy block by pulling it...Ch. 9 - 9. A ball on a string travels once around a circle...Ch. 9 - A sprinter accelerates from rest. Is the work done...
Ch. 9 - 11. A Spring has an unstretched length of 10cm. It...Ch. 9 - 12. The left end of a spring is attached to a...Ch. 9 - The driver of a car traveling at 60 mph slams on...Ch. 9 - Prob. 14CQCh. 9 - Which has the larger kinetic energy, a 10 g bullet...Ch. 9 - At what speed does a 1000 kg compact car have the...Ch. 9 - 3. A mother has four times the mass of her young...Ch. 9 - 4. A horizontal rope with 15 N tension drags a 25...Ch. 9 - 5. A 25 kg box sliding to the left across a...Ch. 9 - A 2.0 kg book is lying on a 0.75-m-high table. You...Ch. 9 - Prob. 7EAPCh. 9 - Prob. 8EAPCh. 9 - 9. You throw a 5.5 g coin straight down at 4.0 m/s...Ch. 9 - Prob. 10EAPCh. 9 - 12. Evaluate the dot product if
and .
and .
Ch. 9 - 12. Evaluate the dot product if
and .
and .
Ch. 9 - 13. What is the angle ? between vectors and in...Ch. 9 - Prob. 14EAPCh. 9 - Prob. 15EAPCh. 9 - 16. A 25 kg air compressor is dragged up a rough...Ch. 9 - Prob. 17EAPCh. 9 - The two ropes seen in FIGURE EX9.18 are used to...Ch. 9 - 19. The three ropes shown in the bird’s-eye view...Ch. 9 - Prob. 20EAPCh. 9 - Prob. 21EAPCh. 9 - Prob. 22EAPCh. 9 - A particle moving on the x-axis experiences a...Ch. 9 - Prob. 24EAPCh. 9 - A horizontal spring with spring constant 750 N/m...Ch. 9 - 26. A 35-cm-long vertical spring has one end fixed...Ch. 9 - A 10-cm-long spring is attached to the ceiling....Ch. 9 - A 60 kg student is standing atop a spring in an...Ch. 9 -
29. A 5.0 kg mass hanging from a spring scale is...Ch. 9 - A horizontal spring with spring constant 85 N/m...Ch. 9 - 31. One mole (6.02 × 1023 atoms) of helium atoms...Ch. 9 - 32. A 55 kg softball player slides into second...Ch. 9 - A baggage handler throws a 15 kg suitcase along...Ch. 9 -
34. An 8.0 kg crate is pulled 5.0 m up a 30°...Ch. 9 - Justin, with a mass of 30 kg, is going down an...Ch. 9 - Prob. 36EAPCh. 9 - Prob. 37EAPCh. 9 - 38. How much energy is consumed by (a) a 1.2 kW...Ch. 9 - 39. At midday, solar energy strikes the earth with...Ch. 9 - Prob. 40EAPCh. 9 - Prob. 41EAPCh. 9 - Prob. 42EAPCh. 9 - 43. A 1000 kg elevator accelerates upward at 1.0...Ch. 9 - 44. a. Starting from rest, a crate of mass m is...Ch. 9 - Prob. 45EAPCh. 9 - 46. A particle of mass m moving along the x-axis...Ch. 9 -
47. A ball shot straight up with kinetic energy...Ch. 9 - 48. A pile driver lifts a 250 kg weight and then...Ch. 9 - Prob. 49EAPCh. 9 -
50. You’re fishing from a tall pier and have...Ch. 9 - Hook’s law describes an ideal spring. Many real...Ch. 9 -
52. The force acting on a particle is Fx =...Ch. 9 - 53. The gravitational attraction between two...Ch. 9 -
54. An electric dipole consists of two equal...Ch. 9 - Prob. 55EAPCh. 9 -
56. When a 65 kg cheerleader stands on a...Ch. 9 - Prob. 57EAPCh. 9 - Prob. 58EAPCh. 9 -
59. A horizontal spring with spring constant 250...Ch. 9 - 60. A 90 kg firefighter needs to climb the stairs...Ch. 9 - Prob. 61EAPCh. 9 - 62. When you ride a bicycle at constant speed,...Ch. 9 -
63. A farmer uses a tractor to pull a 150 kg...Ch. 9 - Prob. 64EAPCh. 9 - Prob. 65EAPCh. 9 - Prob. 66EAPCh. 9 - In problems 67 through 69 you are given the...Ch. 9 - Prob. 68EAPCh. 9 - Prob. 69EAPCh. 9 - Prob. 70EAPCh. 9 - Prob. 71EAPCh. 9 - Prob. 72EAP
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- Suppose the ski patrol lowers a rescue sled and victim, having a total mass of 90.0 kg, down a 60.0° slope at constant speed, as shown in Figure 7.37. The coefficient of friction between the sled and the snow is 0.100. (a) How much work is done by friction as the sled moves 30.0 m along the hill? (b) How much work is done by the rope on the sled in this distance? (c) What is the work done by the gravitational force on the sled? (d) What is the total work done?arrow_forwarda shopper in a supermarket pushes a cart with a force of 35 N directed at an angle of 25 below the horizontal. The force is just sufficient to overcome various frictional forces, so the cart moves at constant speed, (a) Find the work done by the shopper as she moves down a 50.0-m length aisle, (b) What is the net work done on the cart? Why? (c) The shopper goes down the next aisle, pushing horizontally and maintaining the same speed as before. If the work done by frictional forces doesnt change, would the shoppers applied force be larger, smaller, or the same? What about the work done on the cart by the shopper?arrow_forwardAs a simple pendulum swings back and forth, the forces acting on the suspended object are the force of gravity, the tension in the supporting cord, and air resistance, (a) Which of these forces, if any, does no work on the pendulum? (b) Which of these forces does negative work at all times during the pendulums motion? (c) Describe the work done by the force of gravity while the pendulum is swinging.arrow_forward
- Give an example of a situation in which there is a force and a displacement, but the force does no work. Explain why it does no work.arrow_forwardPhysics Review A team of huskies performs 7 440 J of work on a loaded sled of mass 124 kg, drawing it from rest up a 4.60-m high snow-covered rise while the sled loses 1 520 J due to friction, (a) What is the net work done on the sled by the huskies and friction? (b) What is the change in the sleds potential energy? (c) What is the speed of the sled at the top of the rise? (See Section 5.5.)arrow_forward(a) What is the average useful power output of a person who does 6.00106 J of useful work in 8.00 h? (b) Working at this rate, how long will it take this person to lift 2000 kg of bricks 1.50 m to a platform? (Work done to lift his body can be omitted because it is not considered useful output here.)arrow_forward
- (a) A force F=(4xi+3yj), where F is in newtons and x and y are in meters, acts on an object as the object moves in the x direction from the origin to x = 5.00 m. Find the work W=Fdr done by the force on the object. (b) What If? Find the work W=Fdr done by the force on the object if it moves from the origin to (5.00 m, 5.00 m) along a straightline path making an angle of 45.0 with the positive x axis. Is the work done by this force dependent on the path taken between the initial and final points?arrow_forwardA particle is subject to a force Fx that varies with position as shown in Figure P7.9. Find the work done by the force on the particle as it moves (a) from x = 0 to x = 5.00 m, (b) from x = 5.00 m to x = 10.0 m, and (c) from x = 10.0 m to x = 15.0 m. (d) What is the total work done by the force over the distance x = 0 to x = 15.0 m?arrow_forwardAs a mass tied to the end of a string strings from its highest point down to its lowest point, it is acted on by three forces: gravity, tension, and air resistance. Which force does (a) positive work? (b) negative work? (c) zero work?arrow_forward
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