Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
第 1 頁,共 7 頁 Print Assignment: Chap7 ::false Chap7 1. Test Bank, Question 25 At time t = 0 a 2-kg particle has a velocity in m/s of At t = 3 s its velocity is During this time the work done on it was: 4J –4 J –12 J –40 J 2. Test Bank, Question 11 An object moves in a circle at constant speed. The work done by the centripetal force is zero because: the displacement for each revolution is zero the average force for each revolution is zero there is no friction the magnitude of the acceleration is zero the centripetal force is perpendicular to the velocity 3. Chapter 7, Concept Question 2 Figure 7-15a shows two horizontal forces that act on a block that is sliding to the right across a frictionless floor. Figure 7-15b shows three plots of the block’s kinetic energy K versus time t. Which of the plots best corresponds to the following three situations: (a) F1 = F2, (b) F1 > F2, (c) F1 < F2? Figure 7-15 http://edugen.wileyplus.com/edugen/shared/assignment/test/agprint.uni?numberQuest=true&title... 2011/10/17 第 2 頁,共 7 頁 Print Assignment: Chap7 ::false (a) F1 = F2 2 (b) F1 > F2 3 (c) F1 < F2 1 1. plot 1 2. plot 2 3. plot 3 4. Test Bank, Question 24 At time t = 0 a particle starts moving along the x axis. If its kinetic energy increases uniformly with t the net force acting on it must be: constant proportional to t inversely proportional to t 5. Test Bank, Question 30 A crate is initially at rest on a horizontal frictionless table. A constant horizontal force F is applied. Which of the following five graphs is a correct plot of work W as a function of crate speed v? I II III IV V http://edugen.wileyplus.com/edugen/shared/assignment/test/agprint.uni?numberQuest=true&title... 2011/10/17 第 3 頁,共 7 頁 Print Assignment: Chap7 ::false 6. Test Bank, Question 4 An object is constrained by a cord to move in a circular path of radius 0.5m on a horizontal frictionless surface. The cord will break if its tension exceeds 16N. The maximum kinetic energy of the object can have is: 4J 8J 16 J 32 J 64 J 7. Test Bank, Question 16 Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope. The coefficient of kinetic friction is 0.05. How much work is done by the campers in pulling the equipment 1000 m if its speed is increasing at the constant rate of 0.20 m/s2? –1.2 × 106 J 1.8 × 105 J 3.0 × 105 J 4.2 × 105 J 1.2 × 106 J 8. *Chapter 7, Problem 43 A force of 5.8 N acts on a 28 kg body initially at rest. Compute the work done by the force in (a) the first, (b) the second, and (c) the third seconds and (d) the instantaneous power due to the force at the end of the third second. (a) Number 0.600714285714 Units J (b) Number 1.802142857143 Units J (c) Number 3.003571428571 Units J (d) Number 3.604285714286 Units W 9. *Chapter 7, Problem 15 The figure shows three forces applied to a trunk that moves leftward by 2.89 m over a frictionless floor. The force magnitudes are F1 = 4.91 N, F2 = 8.92 N, and F3 = 3.06 N, and the indicated angle is θ = 60°. (a) During the displacement, what is the net work done on the trunk by the three applied forces, the gravitational force, and the normal force? (b) Is there a net transfer of energy to or from the trunk? (c) Does the kinetic energy of the trunk increase or decrease? http://edugen.wileyplus.com/edugen/shared/assignment/test/agprint.uni?numberQuest=true&title... 2011/10/17 第 4 頁,共 7 頁 Print Assignment: Chap7 ::false (a) Number (b) to (c) increase 1.300500000000 Units J Significant digits are disabled; the tolerance is +/-5% 10. *Chapter 7, Problem 57 A 265 kg crate hangs from the end of a rope of length L = 13.6 m. You push horizontally on the crate with a varying force to move it distance d = 3.88 m to the side (Fig. 7-43). (a) What is the magnitude of when the crate is in this final position? During the crate's displacement, what are (b) the total work done on it, (c) the work done by the gravitational force on the crate, and (d) the work done by the pull on the crate from the rope? (e) Knowing that the crate is motionless before and after its displacement, use the answers to (b), (c), and (d) to find the work your force does on the crate. Figure 7-43 Problem 57. (a) Number 773.036194532125 (b) Number 0 (c) Number -1467.865346985213 (d) Number 0 (e) Number 1467.865346985213 Units N Units J Units J Units J Units J 11. Test Bank, Question 49 Three identical springs (X,Y,Z) are arranged as shown. When a 4.0-kg mass is hung on X, the mass descends 3.0 cm. When a 6.0-kg mass is hung on Y, the mass descends: http://edugen.wileyplus.com/edugen/shared/assignment/test/agprint.uni?numberQuest=true&title... 2011/10/17 第 5 頁,共 7 頁 Print Assignment: Chap7 ::false 2.0 cm 4.0 cm 4.5 cm 6.0 cm 9.0 cm 12. *Chapter 7, Problem 27 A spring and block are in the arrangement of Fig. 7-11. Fig. 7-11 When the block is pulled out to x = +4.0 cm, we must apply a force of magnitude 370 N to hold it there. We pull the block to x = 12.0 cm and then release it. How much work does the spring do on the block when the block moves from xi=+6.0 cm to (a)x= +4.0 cm, (b)x=-4.0 cm, (c)x=-6.0 cm, and (d)x=-9.0 cm? (a) Number 9.25 Units J http://edugen.wileyplus.com/edugen/shared/assignment/test/agprint.uni?numberQuest=true&title... 2011/10/17 第 6 頁,共 7 頁 Print Assignment: Chap7 ::false (b) Number 9.25 Units J (c) Number 0 (d) Number -20.8125 Units J Units J 13. *Chapter 7, Problem 62 A 210 g block is dropped onto a relaxed vertical spring that has a spring constant of k = 3.9 N/cm (Fig. 7-44). The block becomes attached to the spring and compresses the spring 11 cm before momentarily stopping. While the spring is being compressed, what work is done on the block by (a) the gravitational force on it and (b) the spring force? (c) What is the speed of the block just before it hits the spring? (Assume that friction is negligible.) (d) If the speed at impact is doubled, what is the maximum compression of the spring? Fig. 7-44 Problem 62. (a) Number 0.22638 Units J (b) Number -2.3595 Units J (c) Number 4.507263978450 Units m/s (d) Number 0.214523556525 Units m 14. *Chapter 7, Problem 61 What work is done by a force m) + (6 m) Number -256 to a position = (7x N) f = -(5 m) + (6 N) , with x in meters, that moves a particle from a position i = (9 - (4 m) ? Units J Significant digits are disabled; the tolerance is +/-5% 15. *Chapter 7, Problem 41 A single force acts on a 1.0 kg particle-like object in such a way that the position of the object as a function of time is given by x = 1.5t - 0.86t2 + 3.8t3, with x in meters and t in seconds. Find the work done on the object by the force from t = 0 to t = 8.5 s. Number 328478.31545 Units J Significant digits are disabled; the tolerance is +/-5% http://edugen.wileyplus.com/edugen/shared/assignment/test/agprint.uni?numberQuest=true&title... 2011/10/17 第 7 頁,共 7 頁 Print Assignment: Chap7 ::false 16. *Chapter 7, Problem 48 A 0.29 kg ladle sliding on a horizontal frictionless surface is attached to one end of a horizontal spring (k = 220 N/m) whose other end is fixed. The ladle has a kinetic energy of 16 J as it passes through its equilibrium position (the point at which the spring force is zero). (a) At what rate is the spring doing work on the ladle as the ladle passes through its equilibrium position? (b) At what rate is the spring doing work on the ladle when the spring is compressed 0.090 m and the ladle is moving away from the equilibrium position? (a) Number 0 Units W (b) Number -202.115234457970 Units W http://edugen.wileyplus.com/edugen/shared/assignment/test/agprint.uni?numberQuest=true&title... 2011/10/17