7/26/2019 Fisika_dasar_-_Usaha_1

1/3

AP PhysicsTest - Work, Energy, and Conservation of Energy

Part I. Multiple Choice (5 points each)Choose the one best answer to each of the following problems.

1 (AP). 0 5 10 15

10

5

0

P

Q

FyFx

The constant force F with components Fx= 3 Newtons and Fy= 4 Newtons, shown above, acts on a body

while that body moves from point P (x=2 meters, y = 6 meters) to the point Q (x = 14 m, y = 1 m). Howmuch work does the force do on the body during this process?a) 16 J b) 30 J c) 46 J d) 56 J e) 65 J

2 (AP). An object of mass m is lifted at constant velocity a vertical distance H in time T. The powersupplied by the lifting force is:a) mgHT b) mgH/T c) mg/HT d) mgT/H e) zero

3 (AP). A ball is thrown upward. At a height of 10 meters above the ground, the ball has a potential

energy of 50 joules (with the potential energy equal to zero at ground level) and is moving upward witha kinetic energy of 50 joules. Air friction is negligible. The maximum height reached by the ball is mostnearly:a) 10 m b) 20 m c) 30 m d) 40 m e) 50 m

4 (AP). From the top of a 70 m high building, a 1-kg ball is thrown directly downward with an initialspeed of 10 m/s. If the ball reaches the ground with a speed of 30 m/s, the energy lost to friction is mostnearly:a) 0 J b) 100 J c) 300 J d) 400 J e) 700 J

5. Two vectors Aand Bare given by A= 5i+ 6j+ 7kand B= 3i- 8j+ 2k. If these two vectors are drawnstarting at the same point, what is the angle between them?a) 106 b) 102 c) 110 d) 113 e) 97

7/26/2019 Fisika_dasar_-_Usaha_1

2/3

6.

37

16 N

A 3.0 kg block is dragged over a rough horizontal surface by a constant force of 16 N acting at an angle of37 above the horizontal as shown above. The speed of the block increases from 4.0 m/s to 6.0 m/s in adisplacement of 5.0 m. What work was done by the friction force during this displacement?a) -34 J b) -64 J c) 30 J d) -94 J e) + 64 J

7. A certain pendulum consists of a 1.5 kg mass swinging at the end of a string (length = 2.0 m). At thelowest point in the swing the tension in the string is equal to 20 N. To what maximum height above thislowest point will the mass rise during its oscillation?a) 77 cm b) 50 cm c) 63 cm d) 36 cm e) 95 cm

8.

2.0 kg

3.0 kg

The two masses in the figure above are released from rest. After the 3.0 kg mass has fallen 1.5 m, it ismoving with a speed of 3.8 m/s. How much work is done during this time interval by the frictional forceon the 2.0 kg mass?a) -12 J b) -17 J c) -20 J d) -8 J e) -28 J

Part II. Free Response Questions (15 points each)Answer each of the following problems in as much detail as possible, being sure to show all work!

9 (AP).

20 kg

k = 200 N/m

6 m30

A 20-kg mass, released from rest, slides 6 meters down a frictionless plane inclined at an angle of 30with the horizontal and strikes a spring of spring constant k = 200 N/m as shown in the diagram above.Assume that the spring is ideal, that the mass of the spring is negligible, and that mechanical energyis conserved.a. Determine the speed of the block just before it hits the spring.

7/26/2019 Fisika_dasar_-_Usaha_1

3/3

b. Determine the distance the spring has been compressed when the block comes to rest.

c. Is the speed of the block a maximum at the instant the block strikes the spring? Justify your answer.

10. When an automobile moves with constant velocity, the power developed is used to overcome thefrictional forces exerted by the air and the road. If the power developed in an engine is 50.0 hp, whattotal frictional force acts on the car at 55 miles per hour? (One horsepower = 746 W.)

11. A 1.2 kg block sliding on a horizontal frictionless surface is attached to one end of a horizontalspring (k = 200 N/m) which has its other end fixed. The block is displaced 0.20 m horizontally from itsequilibrium position and released from rest. What is the speed of the block when it is 0.10 m from itsequilibrium position?

12. A 2.0 kg mass is projected vertically upward from ground level with an initial speed of 30 m/s. themass rises to a maximum height of 35 m above ground level. How much work is done on the mass by airresistance between the point of projection and the point of maximum height?