Describing Motion

Select the best possible answer.

1. Suppose we choose inches as our basic unit of distance and days as our basic unit of time. What would the units of velocity and acceleration be in this system?

a. The unit for velocity is in/s² and for acceleration is in/s.

b. The unit for velocity is in/s and for acceleration is in/s².

c. The unit for velocity is in/day and for acceleration is in/day².

d. The unit for velocity is in/day² and for acceleration is in/day.

2. What does the speedometer of a car measure?

a. The average speed of a car.

b. The instantaneous speed of a car.

c. The average acceleration of a car.

d. The distance traveled by a car.

3. A car traveling around a circular track moves with a constant speed of 100 km/h. Is this car moving with constant velocity?

a. Yes: because the speed remains constant as it moves.

b. Yes: because the track's radius of curvature remains constant.

c. No: because the direction of motion of the car changes continuously.

d. No: because the distance traveled by the car is not constant.

4. A car traveling around a circular track moves with a constant speed of 100 km/h. Is this car accelerating?

a. Yes: because the direction of the velocity is changing.

b. Yes: because a car always accelerates around a racetrack.

c. No: because the speed remains constant at 100 km/h.

d. No: because the velocity vector remains in a constant direction.

5. A ball is tied to a string fastened at the other end to a rigid support forms a pendulum. If we pull the ball to one side and release it, the ball moves back and forth along an arc determined by the length of the string. Which one of the following statements is correct?

a. The speed and the velocity of the ball remain constant throughout its motion.

b. The speed and the velocity keep and changing and are not constant during the motion.

c. The speed remains constant but the velocity changes because of change in direction.

d. The velocity remains constant but the speed changes as the motion slows down and speeds up.

6. A dropped ball gains speed at it falls. Can the velocity of the ball be constant in this motion?

a. The velocity is constant because the direction of motion is constant.

b. The velocity is constant because speed is constant.

c. The velocity is not constant because the speed is increasing.

d. We cannot say because we do not know the acceleration of the ball.

7. A driver of a car steps on the brakes, causing the speed of the car to decrease. Does the car accelerate?

a. The car accelerates due to the change in its velocity.

b. The car is slowing down, thus it cannot have any acceleration.

c. The velocity remains in the same direction and the acceleration is zero.

d. There is a change in speed but that is not enough to produce an acceleration for the car.

8. At a given instant of time, two cars traveling at different speeds, one twice as large as the other. Based upon this information which car has the larger acceleration at this instant of time?

a. The car with twice the speed must have twice the acceleration of the other car.

b. The acceleration of both cars is zero at that instant of time.

c. We cannot say because the values for the speeds of the car are not given.

d. There is not enough information to determine the acceleration of the cars.

9. In the graph shown here, velocity is plotted as a function of time for an object traveling in a straight line. Is the velocity constant for any time interval shown?

a. The velocity is changing at all instants of time.

b. The velocity is constant during the instant of t = 0 and t = 2 seconds.

c. The velocity is constant during the instant of t = 2 to t = 4 seconds.

d. The velocity is constant during the instant of t = 4 to t = 8 seconds.

10. A car moves along a straight line so that position varies with time as shown in the figure. Does the car ever go backward?

a. The car is going backward in the third segment of its motion.

b. The car is always going forward because the distance is constantly increasing.

c. The car travels backward during the second segment of its motion.

d. The car travels backward during the first segment of its motion.

11. In the car of the previous question, how does the instantaneous speed at point A compares to point B?

a. Instantaneous speed at A is greater than instantaneous speed at point B.

b. Instantaneous speed at A is less than instantaneous speed at point B.

c. Instantaneous speed at A is equal to the instantaneous speed at point B.

d. We cannot say because the time of travel for each segment is not given.

12. For the car of the previous problem, is the velocity constant during any time interval shown?

a. Since the distance is changing the velocity in each time interval is not constant.

b. The velocity is constant during the first time interval but not during the second and third intervals.

c. The velocity remains constant during the first and second intervals but not in the third interval.

d. The velocity remains constant in each of the three time intervals.

13. A car moves along a straight section of road so that its velocity varies with time as shown in the graph. Does the car ever go backward?

a. The car goes forward in all three-time intervals shown in the figure.

b. The car goes forward in the first and second time interval but backward in the third time interval.

c. The car goes forward in the first time interval and backward in the second and third time intervals.

d. The car goes backward in the first time interval but forward in the second and third time intervals.

14. For the car whose velocity is plotted in the previous question, in which time interval the acceleration is zero?

a. The acceleration is zero in all three-time intervals.

b. The acceleration is zero in the second time but none zero in the first and third intervals.

c. The acceleration is zero in the first interval but none zero in second and third intervals.

d. The acceleration is not zero in any of the three time intervals.

15. A car traveling in the forward direction experiences a negative acceleration for 10 seconds. Is the distance covered in the first 5 seconds equal to, greater than, or less than the distance traveled during the second 5 seconds?

a. The distance traveled during the first 5 seconds is the same as the second 5 seconds.

b. The distance traveled during the first 5 seconds is greater than the second 5 seconds.

c. The distance traveled during the first 5 seconds is less than the second 5 seconds.

d. The distance traveled in the second 5 seconds is zero because of the zero acceleration.

16. The velocity-versus-time graph of an object curves as shown in the diagram. Is acceleration of the object constant?

a. Yes; the curve is a smooth curve indicating a constant acceleration.

b. Yes; acceleration is constant because the curve seems to be leveling off.

c. No; for a constant acceleration, the graph has to be a horizontal line.

d. No; for a constant acceleration, the graph has to be a line of constant slope.

17. The two measurements necessary for calculating average speed are:

a. Acceleration and time.

b. Velocity and time.

c. Distance and time.

d. Distance and acceleration.

18. A traveler covers a distance of 460 miles in 8 hours. What is the average speed of this trip?

a. 460 mph.

b. 57.5 mph.

c. 460 miles/h².

d. 57.5 miles/h².

19. A driver drives for 3.5 hours at an average speed of 58 mph. What distance does she travel in this time?

a. 203 miles.

b. 58 miles.

c. 203 mph.

d. 58 mph.

20. A car travels with an average speed of 25 m/s. What is the speed in km/h?

a. 25000 km/h.

b. 90000 km/h.

c. 90 km/h.

d. 60 km/h.

21. The velocity of a car decreases from 30 m/s to 18 m/s in a time of 4 seconds. What is the average acceleration of the car in this trip?

a. 3 m/s.

b. 3 m/s².

c. -3 m/s².

d. 3 m.

22. A car traveling with an initial speed of 12 m/s accelerates at a constant rate of 2.5 m/s² for 2 seconds. What is the velocity at the end of this time?

a. 12 m/s.

b. 17 m/s.

c. 2.5 m/s.

d. 14.5 m/s.

23. What is the distance traveled by the car of the previous question.

a. 24 m.

b. 29 m.

c. 5 m.

d. 17 m.

24. A runner moving with an initial velocity of 9 m/s slows down at a constant rate of 1.5 m/s² over a period of 2 seconds. What is the velocity at the end of this time?

a. 6 m/s.

b. 9 m/s.

c. 7.5 m/s.

d. 10.5 m/s.

25. What is the distance traveled by the runner of the previous problem?

a. 18 m.

b. 21 m.

c. 15 m.

d. 5 m.

26. If a car increases its velocity from zero to 60 km/h in 10 seconds, its acceleration is,

a. 3 km/h/s.

b. 6 km/h/s.

c. 10 km/h/s.

d. 60 km/h/s.

27. If a rocket initially at rest accelerates at a rate of 50 m/s², what is its speed after 1 minute?

a. 50 m/s.

b. 500 m/s.

c. 3000 m/s.

d. 3600 m/s.

28. While a car travels around a circular track at constant speed, which of the following statements is true?

a. Acceleration of the car is zero.

b. Velocity of the car is zero.

c. Both (a) and (b).

d. None of these.

29. A car accelerates from rest at 2 meters per second per second (i.e. 2 m/s²). What is its speed 3 seconds after the car starts moving?

a. 2 m/s.

b. 3 m/s.

c. 4 m/s.

d. 6 m/s.

30. For the car of the previous question, how long will it take for the car's speed to reach 30 m/s?

a. 2 s.

b. 15 s.

c. 30 s.

d. 60 s.

31. What is the acceleration of a car that maintains a constant velocity of 100 km/h for 20 seconds?

a. 0.

b. 100 km/h/s.

c. 5 km/h/s.

d. 120 km/h.