Physics 101
World Wide Web Example Exam IV

Answers can be found here.

1. What impulse is needed to stop a 1200-kg car traveling at 20 m/s?
(a) 20 N.s
(b) 1200 N.s
(c) 60 N.s
(d) 24,000 N.s

2. A force times time is most appropriately called
(a) a torque
(b) an impulse
(c) an angular momentum
(d) a change in momentum

3. Which of the following is true about momentum?
(a) it is a vector
(b) it is a product of mass times velocity
(c) impulses are required to change it
(d) all of the above
(e) none of the above

4. A car with a mass of 2000 kg moves at 10 m / s. Calculate the braking force needed to bring the car to a halt in 5 seconds.
(a) 100000N
(b) 4000N
(c) 20000N
(d) 40 N

5. The car moving at 50 kilometers/hour skids 10 meters with locked brakes. How far will the car skid with locked brakes if it is traveling at 150 kilometers/hour?
(a) 20 meters
(b) 60 meters
(c) 90 meters
(d) 120 meters
(e) 180 meters

6. At what point in its motion is the kinetic energy of a pendulum bob a minimum?
(a) at the highest points in its motion
(b) at the lowest point in its motion
(c) half way between the highest and lowest points in its motion

7. A 1-kg object rests on a table 1 m above the floor. What is the gravitational potential energy in Joules of the object with respect to the floor?
(a) 1 (b) 9.8 (c) 32
(d) 11.8 (e) 0

8. When a car is braked to a stop, its kinetic energy is transformed to
(a) stopping energy.
(b) potential energy.
(c) heat energy.
(d) energy of rest.

9. If you push on an immovable wall for an hour, is there any work done on the wall?
(a) Yes (b) No

10. Can a body have kinetic energy without having momentum?
(a) Yes (b) No

11. A torque acting on an object tends to produce
(a) equilibrium.
(b) rotation.
(c) linear motion.
(d) stability.

12. A coin and a ring roll down an incline starting at the same time from rest. The one to reach the bottom first will be the
(a) ring
(b) coin
(c) both reach the bottom at the same time

13. The center of mass of a body can be outside of the body
(a) True (b) False

14. When a spinning ice skater draws her arms in close to her body, she starts to spin faster. This is an example of
(a) external torque friction
(b) Newton's second law
(c) conservation of angular momentum
(d) spin impulse

15. Which is the larger force?
(a) the force that the earth exerts on the moon
(b) the force that the moon exerts on the earth
(c) neither

16. A merchant of gold should_________ at a high altitude and ___________ at a low altitude.
(a) buy, sell
(b) sell, buy
(c) buy or sell, buy or sell

17. When the distance between two stars decreases by half, the force between them
(a) decreases by one-quarter
(b) decreases by one-half
(c) increases to twice as much
(d) increases to four times as much
(e) stays the same

18. The planet Jupiter is about 300 times as massive as earth, yet on its surface you would weight only about 3 times as much. This is because
(a) your mass is 100 times less on Jupiter.
(b) Jupiter is significantly farther from the sun.
(c) Jupiter's radius is 10 times the earth's radius.
(d) you are 100 times more weightless there.
(e) none of these.
19. Inside a freely-falling elevator, there would be no
(a) gravitational force on you.
(b) apparent weight for you.
(c) both of these
(d) none of these

20. Which is most responsible for the ocean tides?
(a) ships
(b) continental drift
(c) the moon
(d) the sun

21. Padded dashboards in cars are safer in an accident than nonpadded ones because an occupant hitting the dash has
(a) increased time of impact.
(b) decreased impulse.
(c) decreased impact force.
(d) a and b above.
(e) a and c above.

22. Two identical gliders slide toward each other on an air track. One moves at 1 m/s and the other at 2 m/s. They collide and stick. The combined mass moves at
(a) 3/4 m/s.
(b) 1/3 m/s.
(c) 1/6 m/s.
(d) 1/2 m/s.
(e) 1.5 m/s.

23. A 5-kg fish swimming at a speed of 1 m/s swallows an absent-minded 1-kg fish at rest. The speed of the larger fish after lunch is
(a) 1/2 m/s.
(b) 2/5 m/s.
(c) 5/6 m/s.
(d) 6/5 m/s.
(e) 1 m/s.

24. A moving object on which no forces are acting will continue to move with constant
(a) impulse.
(b) momentum.
(c) acceleration.
(d) all of these
(e) none of these.

25. When you are in the way of a fast-moving object and can't get out of its way, you will suffer a smaller force of impact if you decrease its momentum over a
(a) short time.
(b) long time.
(c) same way either way.

26. When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, you make the time of the impact about 10 times as great as for a stiff-legged landing. In this way the average force your body experiences is
(a) less than 1/10 as great.
(b) about 1/10 as great.
(c) about 10 times as great.
(d) more than 1/10 as great.

27. If you push an object with twice the work input for twice the time, your power input is
(a) four times as much.
(b) twice.
(c) the same amount as for half the work in half the time.

28. Whereas impulse involves the time that a force acts, work involves the
(a) time and distance that a force acts.
(b) distance that a force acts.
(c) acceleration that a force produces.

29. An object that has kinetic energy must be
(a) falling.
(b) moving.
(c) at an elevated position.
(d) at rest.
(e) none of these.

30. Do 100 J of work in 50 s and your power output is
(a) 1/4 W.
(b) 1/2 W.
(c) 2 W.
(d) 4 W.
(e) more than 4 W.

31. Put a pipe over the end of a wrench when trying to turn a stubborn nut on a bolt, to effectively make the wrench handle twice as long, you'll multiply the torque by
(a) two.
(b) four.
(c) eight.

32. A car travels in a circle with constant speed. The net force on the car is
(a) zero because the car is not accelerating.
(b) directed towards the center of the curve.
(c) directed forward, in the direction of travel.
(d) none of these.

33. The reason the moon does not crash into the earth is that the
(a) moon has less mass than the earth.
(b) earth's gravitational field is weak at the moon.
(c) gravitational pull of other planets keeps the moon up.
(d) moon has a sufficient tangential speed.
(e) none of these.