ch 5 review
Modified True/False
Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true.
____
1. Force is the ability to change motion. _________________________
____
2. Weight is a force due to gravity pulling on any object with mass. _________________________
____
3. Tension is a contact force. _________________________
____
4. By compressing a spring, you increase its length. _________________________
____
5. A moving object slows to a stop because of compression. _________________________
____
6. The greater the force squeezing two surfaces together, the smaller the friction force.
_________________________
____
7. Lubrication reduces the friction between machine parts. _________________________
____
8. A zero net force causes an acceleration. _________________________
____
9. If an object is at rest, the net force on it must be unbalanced. _________________________
Completion
Complete each statement.
Select the correct term to complete each sentence. There are extra terms in the list.
greater than
vector
tension
newton
net
less than
scalar
compression
pound
equilibrium
equal to
friction
normal
kilogram
free-body
10. If you traveled to Mars, your mass would be _________________________ than your mass on Earth.
11. Force is a(n) ____________________ because it has both an amount and a direction.
12. The _________________________ is the English unit of weight equal to about 0.454 kg of mass.
13. The SI unit of force required for a 1-kg object to accelerate at 1 m/s2 is the _________________________.
14. A force that resists the motion of objects or surfaces as they move over one another is called
____________________.
15. The force exerted by a surface on an object that is pressing on it is the ____________________ force.
16. The force which is the sum of all forces acting on a object is called ____________________ force.
17. A diagram shows all the forces acting on an object is a _________________________ diagram.
Short Answer
An astronaut brings her lucky horseshoe on a mission to the Moon. Answer the following questions about this
horseshoe.
18. Would the lucky horseshoe’s mass on the Moon be the same, greater than, or less than the mass of the
horseshoe when it is on the Earth? Explain your answer.
19. Describe one similarity and one difference between friction and gravity.
20. Why does it take longer for a skidding car to stop on an icy road than on a dry road?
Problem
The table below gives the gravitational force for different planets in our solar system.
Planet
Mercury
Venus
Earth
Neptune
Jupiter
Gravitational Force
(N/kg)
3.7
8.9
9.8
11.0
23.1
21. Sophie has a mass of 50.0 kg. Using the table above, what would her weight be on Jupiter?
22. A 400-kg space probe has a weight of 3,560 N on one of the above planets. According to the table above, on
which planet is the space probe? Show your work.
23. The diagram below represents an object moving to the right with a constant velocity.
What is the value of force F?
Figure 5-1
This box is being acted upon by forces in the up, down, left, and right directions. Use this diagram to answer
the following questions.
24. Calculate the net force on the box shown in Figure 5-1.
25. Is the box Figure 5-1 accelerating? If not, what type of motion does it have?
Essay
26. An empty wagon rolls easily, but a loaded wagon is more difficult to roll. Using your knowledge of friction
force and weight, explain why this is so.
27. Jim and his friend Bill are building a small pond on their farm by piling rocks across the channel of a stream
to make a dam. If they have difficulty lifting a rock out of the water to move it to the dam, they carry the rock
more easily by keeping it under the surface of the water. Explain why this works.
Other
28. Draw a diagram showing two 10-newton forces acting on a block that is NOT in equilibrium. Draw a second
diagram showing two 10-newton forces acting on a block that IS in equilibrium.
ch 5 review
Answer Section
MODIFIED TRUE/FALSE
1. ANS:
REF:
2. ANS:
REF:
3. ANS:
REF:
4. ANS:
T
section 5.1
T
section 5.1
T
section 5.1
F, decrease
PTS: 1
DIF:
basic
PTS: 1
DIF:
basic
PTS: 1
DIF:
basic
DIF:
basic
PTS: 1
5. ANS: F, friction
DIF: basic
REF: section 5.1
PTS: 1
6. ANS: F
larger
greater
DIF: basic
REF: section 5.2
PTS: 1
7. ANS: T
REF: section 5.2
8. ANS: F
unbalanced
nonzero
DIF: basic
REF: section 5.2
PTS: 1
PTS: 1
9. ANS: F
balanced
zero
DIF: basic
REF: section 5.3
PTS: 1
DIF: basic
REF: section 5.3
PTS: 1
11. ANS: vector
DIF: basic
REF: section 5.1
PTS: 1
12. ANS:
pound
lb
DIF: basic
REF: section 5.1
COMPLETION
10. ANS: equal to
PTS: 1
13. ANS:
newton
N
DIF: basic
REF: section 5.1
PTS: 1
14. ANS: friction
DIF: basic
REF: section 5.1
PTS: 1
15. ANS: normal
DIF: basic
REF: section 5.2
PTS: 1
16. ANS: net
DIF: basic
REF: section 5.3
PTS: 1
17. ANS:
free-body
free body
DIF: basic
REF: section 5.3
DIF: basic
REF: section 5.3
PTS: 1
SHORT ANSWER
18. ANS:
The mass of the horseshoe would be the same. Mass is a measure of the amount of matter in an object, and the
amount of matter in the horseshoe does not change when it is taken from one place to another.
PTS: 1
DIF: intermediate REF: section 5.1
19. ANS:
Similarity: Friction and gravity are both forces.
Difference: Friction is a contact force and gravity is an at-a-distance force.
PTS: 1
DIF: intermediate REF: section 5.1
20. ANS:
The ice reduces the friction between the tire and the road.
PTS: 1
PROBLEM
21. ANS:
DIF: advanced
REF: section 5.2
PTS: 1
22. ANS:
Venus
DIF: intermediate
REF: section 5.1
The planet with a gravitational force of 8.9 kg/N is Venus.
PTS: 1
DIF: advanced
REF: section 5.1
23. ANS:
In order for the box to move at a constant velocity, it must be in equilibrium with a net force of zero.
Therefore, the force F pulling to the left must balance the 6 N force pulling to the right.
F=6N
PTS: 1
DIF: advanced
REF: section 5.3
24. ANS:
The net force is zero. All the forces cancel out: There are 10 N pushing to the right and 10 N pushing to the
left. There are 6 N pushing up and 6 N pushing down.
PTS: 1
DIF: intermediate
25. ANS:
No, the box is not accelerating because the net force is zero. It must either be at rest or moving at constant
velocity.
PTS: 1
DIF: intermediate
REF: section 5.3
ESSAY
26. ANS:
The frictional force between two surfaces is proportional to the force pushing them together. As weight is
added to a wagon, the wheels of the wagon and the surface on which it rolls are pushed together with greater
force. This increases the frictional force, making it more difficult to roll the wagon
PTS: 1
DIF: intermediate REF: section 5.2
27. ANS:
Since the rock is more dense than water, it will naturally tend to stay submerged under the surface. To pick
the rock up completely out of the water requires a force equal to the entire weight of the rock. If the rock is
lifted just enough to get it off the bottom of the stream but it still remains under the surface of the water, the
buoyant force of the water will reduce the force the boys have to exert to lift the rock.
PTS: 1
OTHER
28. ANS:
DIF: intermediate
REF: section 10.4
PTS: 1
DIF: intermediate
REF: section 5.3