1. Motion Study Guide
Answer Key

2. 1. How can you determine if an object is in motion?
If an object changes position it is in motion. Change in position can be determined using a reference point.

3. 2. To calculate speed you must know what two quantities?
Distance and time

4. 3. How is velocity different than speed?
Velocity includes speed AND direction.

5. 4. What are the correct SI units for speed?
Meters/second (m/s)

6. 5. What are the correct SI units for distance?
Meters (m)

7. 6. What are the correct SI units for acceleration?
Meters/second squared (m/s2)

8. 7. What does a flat line on a DISTANCE-time graph indicate?
No motion

9. 8. What does a flat line on a SPEED-time graph indicate?
Constant speed

10. 9. What is the difference in instantaneous & average speed?
Instantaneous speed is the speed of the object at one particular moment in time. Average speed is the total distance traveled in the total amount of time.

11. 10. How can objects experience acceleration?
Speed up, slow down, & change direction

12. 11. How does mass affect acceleration?
Increasing mass decreases acceleration.
Decreasing mass increases acceleration.

13. 12. How does force affect acceleration?
Increasing force increases acceleration.
Decreasing force decreases acceleration.

14. The tendency of an object to resist a change in motion.
13. Describe inertia.
The tendency of an object to resist a change in motion.

15. 14. Give an example of inertia.
A book sitting on a desk will continue to sit on the desk until a force moves it.

16. How hard it is to stop an object that is in motion.
15. Define momentum.
How hard it is to stop an object that is in motion.

17. 16. How do you know if an object will have a great momentum?
If the object has a large mass or high velocity, momentum will be greater.

18. 17. Explain the Law of Conservation of Momentum.
The total momentum of a group of objects stays the same unless outside forces act on the objects.

19. Positive acceleration is an increase in speed.
18. What is the difference in positive acceleration and negative acceleration/deceleration?
Positive acceleration is an increase in speed.
Negative acceleration/deceleration is a decrease in speed.

20. 19. Define Newton’s 1st Law.
An object in motion will stay in motion and an object at rest will stay at rest unless acted on by an unbalanced force.

21. A golf ball sitting on a tee will stay there until a club hits it.
20. Give an example.
A golf ball sitting on a tee will stay there until a club hits it.

22. 21. Define Newton’s 2nd Law of Motion.
The acceleration of an object depends upon the mass of the object and the force applied.

23. 22. Give an example.
An empty buggy and a full buggy are pushed with the same force. The empty buggy will accelerate more than the full buggy.

24. For every action there is an equal and opposite reaction.
23. Define Newton’s 3rd Law.
For every action there is an equal and opposite reaction.

25. 24. Give an example.
A bat pushes on a ball and the ball pushes back on the bat with the same amount of force.

26. 25. What are the differences between elastic and inelastic collisions?
Elastic collisions occur when objects hit and bounce off of each other.
Inelastic collisions occur when objects hit, stick together, and move as one.

27. In space there is no gravity and no matter to slow them down.
26. Why wouldn’t objects in motion on Earth experience the same forces as they would in space.
In space there is no gravity and no matter to slow them down.

28. 27. What is the net force acting on an object at rest?
Zero

29. 28. How much momentum does a resting object have?
None

30. 29. How much force is applied to a 5 kg object acceleration at 2 m/s2?
F = m x a
F = 5 kg x 2 m/s2
F = 10 N

31. P = m x v P = 10 kg x 3 m/s P = 30 kgxm/s
30. How much momentum does a 10 kg object have that is traveling at 3m/s?
P = m x v
P = 10 kg x 3 m/s
P = 30 kgxm/s

32. 31. What is the speed of an object that travels 20 m in 10 s?
s = d/t
s = 20 m/10s
S = 2 m/s

33. A = vf – vi t A = 15 m/s – 20 m/s 5 s A = -1 m/s2
32. What is the acceleration of an object that starts with an initial speed of 20 m/s and then changes its speed to 15 m/s over 5s?
A = vf – vi t
A = 15 m/s – 20 m/s
5 s
A = -1 m/s2

34. The object is moving at a constant speed.
33. What do you know about the motion of the object from looking at graph 1?
The object is moving at a constant speed.

35. 34. What is the average speed for the object in graph 1?
S = total distance/total time
S = 14 m/100 s
S = 0.14 m/s

36. 35. How far did the object travel in 30 s?
4 m

37. 36. How long did it take the object to travel 10 m?
1.5 s

38. The object speeds up then travels at a constant speed.
37. What do you know about the motion of the object from looking at graph 2?
The object speeds up then travels at a constant speed.

39. Positive acceleration, because the slope of the line is uphill.
38. Is the object experiencing positive or negative acceleration? How do you know?
Positive acceleration, because the slope of the line is uphill.

40. 39. What was the acceleration between 0 & 10 seconds?
A = vf – vi t
A = 16 m/s – 0 m/s
10 s
A = 1.6 m/s2

41. 40. What was the acceleration between 10 s and 20 s?
Zero, object is traveling at a constant speed.