1. Ch. 5 Study Guide
Answer Key

2. 1. What is a reference point
1. What is a reference point? If you are jogging around the track at 6 m/s and pass a student that is walking slowly what is your reference point?
A point you compare an object to, to see if it is in motion; reference point is the student walking.

3. 2. Label the following as a balanced or unbalanced force:
Stroller – unbalanced
child – unbalanced
car – unbalanced
porch swing hanging - balanced

4. 3. List 3 ways to increase friction.
Rougher surface, push objects together, make an object heavier to increase force

5. 4. List 3 ways to decrease friction.
Make surface smoother, decrease force pushing objects together; lubricants

6. 5. How do you calculate speed?
Speed = distance/time

7. A push or pull exerted on an object.
6. What is force?
A push or pull exerted on an object.

8. 7. How do you find net force for forces applied in the same direction
7. How do you find net force for forces applied in the same direction? In opposite directions?
Same direction, forces are added together. Different direction, forces are subtracted.

9. Balanced – zero; unbalanced – not zero
8. What is the net force when forces are balanced? When forces are not balanced?
Balanced – zero; unbalanced – not zero

10. 9. T/F An unbalanced force will always cause a change in speed, direction, or both.
True

11. 10. What type of force can cause a stationary object to begin moving?
Unbalanced

12. Force that opposes motion between two surfaces in contact.
11. What is friction?
Force that opposes motion between two surfaces in contact.

13. Force pushing surfaces together and roughness of the surfaces
12. What two factors determine the amount of friction between two surfaces.
Force pushing surfaces together and roughness of the surfaces

14. 13. List how friction can be helpful and harmful to a car.
Helpful – start and stop the car; harmful – wears down engine

15. 14. How does the mass of an object effect the gravitational force?
More mass an object has, the greater gravitational force.

16. The greater the distance between objects, the less gravitational force
15. How does the distance between two objects effect the gravitational force?
The greater the distance between objects, the less gravitational force

17. 16. Label the following as either characteristics of weight or mass.

18. 17. How do you calculate acceleration?
Acceleration = final velocity – starting velocity/change in time

19. 18 N north – 12 N south = 6 N north
18. What is the net force on an object being pulled 18N north and pulled 12 N south?
18 N north – 12 N south = 6 N north

20. 19. What are the two types of kinetic friction? Describe each.
Sliding friction occurs when surfaces slide over each other (no wheels); rolling friction occurs when wheels roll over a surface.

21. 20. Acceleration changes if the velocity or direction of an object changes.
True

22. 21. What two factors does the law of universal gravitation describe?
The greater the mass of an object the greater the gravitational force. The greater the distance between objects the less the gravitational force

23. Objects change in position relative to a reference point.
22. What is motion?
Objects change in position relative to a reference point.

24. 23. List the SI units for the following terms:
Speed = m/s Acceleration = m/s2

25. 24. How do velocity and speed differ?
Velocity includes direction and speed doesn’t.

26. 25. Tell if the walker’s acceleration is negative or positive.
It is negative because the final velocity is less than the starting velocity. The walker slowed down.

27. 26. Explain how a motion graph would change if an object speeds up, slows, down, or stops.
speeds up = steeper line; slows down = flattened out line; stops = straight line.

28. 28. What is the difference between static and kinetic friction?
Static – not moving; kinetic – moving.