Phys 101 College Physics I Student Name: ______Additional Exercises on Chapter 8: and Conservation of Energy

1) An object of 20.0 kg is lifted vertically through 1.00 m by a 400 N force. How much work is done by the net force in lifting this object? Use g = 10.0 m/s2. A) 40.0 J B) 20.0 J C) 400 J D) 200 J E) 100 J

Figure 8-4

An object of mass 2 kg is held at the top of a triangular wedge as shown in Figure 8 -4, and then released. The reference level for potential energy is at the base of the triangle. Neglect and use g = 10 m/s2.

2) Refer to Figure 8-4. What is the kinetic energy of the object at the top of the wedge? A) 40 J B) 30 J C) 60 J D) 0 J E) 80 J

3) Refer to Figure 8-4. What is the amount of work done by the gravitational force as the object comes to the bottom of the wedge? A) 80 J B) 60 J C) 0 J D) 10 J E) 40 J

A mass of 1.0 kg is pushed against a spring with a spring constant of 25 N/m. As a result, the spring is compressed by 20 cm. The mass is then released.

4) What is the amount of potential energy acquired by the spring when it is compressed? A) 0.20 J B) 0.50 J C) 10 J D) 1.0 J E) 5.0 J

An object of mass 4.00 kg is sitting at the top of an of height h and angle θ with the horizontal. The object slides down the inclined plane and right before it reaches the bottom of the plane, it has of 16.0 m/s. Neglect friction and use g = 10.0 m/s2.

5) What is the height of the inclined plane? A) 128 m B) 16.9 m C) 12.8 m D) 10.0 m E) 25.6 m

6) A force of 15 N applied to a spring stretches it by 4 cm. What is the potential energy of the spring in the stretched position? A) 0.1 J B) 0.2 J C) 0.5 J D) 0.3 J E) 0.4 J

1 7) A force of 4.0 N applied to a spring compresses it by 8.0 cm. What is the amount of work done to compress the spring by an additional amount of 5.0 cm? A) 0.26 J B) 50 N/m C) 2.0 J D) 20 J E) 0.50 J

8) What should the height of a slide in a park be so that a child will reach the bottom of the slide with a speed of 15.0 m/s? Use g = 10.0 m/s2. A) 10.5 m B) 11.3 m C) 15.1 m D) 22.5 m E) 0.75 m

9) As an object of mass 60 kg approaches the bottom of a ramp, point A, its speed is 20 m/s. It goes up the frictionless plane and turns around at point B. What is the potential energy of this object at point B? Use g = 10 m/s2. A) 12 x 103 J B) 0 J C) 6.0 x 103 J D) 9x 103 J E) 18x 103 J

Figure 8-5

A 2.0-g bead slides along a wire, as shown in Figure 8 -5. At point A, the bead is at rest. Neglect friction and use g = 10 m/s2. 10) Refer to Figure 8-5. What is the kinetic energy of the bead at point A? A) 0.40 J B) 2.0 x 10-2 J C) 16 x 10-3 J D) 0 J E) There is not enough information to solve this problem.

11) Refer to Figure 8-5. What is the kinetic energy of the bead at point B? A) 2.0 x 10-2 J B) 0 J C) 0.40 J D) 16 x 10-3 J E) There is not enough information to solve this problem.

2 12) Refer to Figure 8-5. What is the speed of the bead at point C? A) 0 m/s B) 4.0 m/s C) 1.0 m/s D) 2.0 m/s E) There is not enough information to solve this problem.

13) An object of mass 4.0 kg is thrown vertically upwards from ground level with an initial speed of 20 m/s. Ignore friction and use g = 10 m/s2. How high did the object go? A) 4.5 m B) 15 m C) 80 m D) 20 m E) None of the other choices is correct.

Figure 8-6

A roller coaster of mass 80.0 kg is moving with a speed of 20.0 m/s at position A as shown in Figure 8 -6. The vertical height at position A above ground level is 200 m. Neglect friction and use g = 10.0 m/s2.

14) What is the total energy of the roller coaster at point B? A) 20.2 × 103 J B) 16.4 × 103 J C) 16.4 × 104 J D) 17.6 × 104 J E) There is not enough information to solve this problem.

15) What is the speed of the roller coaster at point C? A) 69.2 m/s B) 20.0 m/s C) 34.6 m/s D) 0 m/s E) There is not enough information to solve this problem.

3 An object of mass 2.00 kg is held at a position A, a vertical height of 20.0 m above the ground. Point B is 8.00 m directly below A. Neglect air resistance and use g = 10.0 m/s2.

16) What is the speed of the object just before it touches the ground? A) 12.6 m/s B) 12.0 m/s C) 20.0 m/s D) 10.0 m/s E) There is not enough information to answer this question.

17) An object approaches the bottom of a ramp, point A. It goes up the ramp and turns around at point B, which is 40.0 m above A. The ramp makes an angle of 30.0 ° with the horizontal. What is the speed of the object at point A? Neglect friction and use g = 10.0 m/s2. A) 11.6 m/s B) 15.3 m/s C) 28.3 m/s D) 10.0 m/s E) 23.8 m/s

Figure 8-7

Two M1 = 2.0 kg and M2 = 4.0 kg are attached by a string as shown in Figure 8 -7. M1 falls vertically down and M2 moves on a frictionless surface. Initially the system is at rest. Use g = 10 m/s2.

18) Refer to Figure 8-7. What is the potential energy of the mass M1 just before it touches the ground? A) 2.5 J B) 0 J C) 2.3 J D) 4 J E) 5.2 J

Figure 8-8

19) 6 J of work is needed to push an object of mass 2 kg from point A to point B of the inclined plane as shown in Figure 8-8. If the angle of inclination is 30°, the height of the plane is h, what is the length of the inclined plane? Use g = 10 m/s2. A) 6 m B) 0.6 m C) 0.3 m D) 10 m E) 3 m

4 20) An object of mass 2.00 kg starts at rest from the top of a rough inclined plane of height 20.0 m as shown in Figure 8-8. If the work done by the force of friction is -150 J, what is the speed of the object as it reaches the bottom of the inclined plane? Use g = 10.0 m/s2. A) 200 m/s B) 150 m/s C) 10.0 m/s D) 20.0 m/s E) 15.8 m/s

21) An 8 kg object moving with an initial velocity of 4 m/s comes to rest due to friction after it travels a horizontal distance of 10 m. If the initial speed of the object is doubled, what distance will it travel before coming to rest? Use g = 10 m/s2. A) 80 m B) 30 m C) 40 m D) 20 m E) 10 m

Figure 8-9

An object with a mass of 10.0 kg is at rest at the top of a frictionless inclined plane of height 8.00 m and an angle of inclination 30.0 ° with the horizontal. The object is released from this position and it stops at a distance d from the bottom of the inclined plane along a horizontal surface, as shown in Figure 8 -9. The coefficient of kinetic friction for the horizontal surface is 0.400 and g = 10.0 m/s2.

22) Refer to Figure 8-9. What is the kinetic energy of the object at the bottom of the inclined plane? A) 700 J B) 900 J C) 500 J D) 400 J E) 800 J

23) An object with a mass of 10 kg is moving along a horizontal surface. At a certain point it has 40 J of kinetic energy. If the coefficient of friction between the object and the surface is 0.40, how far will the object go beyond that point before coming to a stop? Use g = 10 m/s2. A) 5.7 cm B) 100 cm C) 17 cm D) 42 cm E) 60 cm

5 Figure 8-11

A 2.0 kg mass is moving along the x axis. The potential energy curve as a function of position is shown in Figure 8 -11. The system is conservative. There is no friction.

24) Refer to Figure 8-11. If the speed of the object at the origin is 4.0 m/s, what will be its speed at 7.0 m along the +x-axis? A) 4.0 m/s B) 4.6 m/s C) 4.4 m/s D) 10 m/s E) 4.1 m/s

6 Answer Key Testname: PHYS 101 ADDITIONAL EXERCISES ON CHAPTER 8

1) D 2) D 3) B 4) B 5) C 6) D 7) A 8) B 9) A 10) D 11) A 12) D 13) D 14) D 15) C 16) C 17) C 18) B 19) B 20) E 21) C 22) E 23) B 24) E

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