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CPS ADV. - McQuaid > Unit 4 Review > Flashcards

Unit 4 Review Flashcards

1
Q

What is a force?

A

A force is a push or a pull

Sometimes, it is obvious that a force has been applied, while other forces are less noticeable.

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2
Q

What does a force cause?

A

A force causes objects to change their motion.

This can include changes in speed, direction, or shape.

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3
Q

What is net force?

A

Net Force is the sum of all forces acting on an object.

It determines the overall effect of all the forces applied.

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4
Q

How are forces measured?

A

Forces are measured in Newtons (N).

The Newton is the standard unit of force in the International System of Units (SI).

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5
Q

What are the three rules for adding forces?

A
  1. Add forces in the same direction.
  2. Subtract forces in opposite directions
  3. Forces not in the same direction or in opposite directions cannot be directly added together

This means that if two forces are acting towards the same point, their magnitudes can be summed.

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6
Q

True or False: Forces not in the same direction or in opposite directions can be directly added together.

A

False

Forces that are not aligned cannot be summed directly.

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7
Q

What type of quantities are forces?

A

Forces are vector quantities.

This means they have both magnitude and direction, similar to displacement.

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8
Q

In a free-body diagram, what does the size of the arrow represent?

A

The magnitude of the force

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9
Q

In a free-body diagram, what does the direction of the arrow indicate?

A

The direction that the force is acting

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10
Q

What is labeled on each force arrow in a free-body diagram?

A

The exact type of force

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11
Q

Fill in the chart with the type of force and what category it belongs to.

The symbols have been left to help you.

A
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12
Q

What is the symbol for Air Resistance Force?

A

Fair

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13
Q

What type of force is Applied Force represented by?

A

Fapp

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14
Q

Which type of force is represented by the symbol Fs?

A

Spring Force

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15
Q

Name three types of action-at-a-distance forces.

A
  • Gravitational Force (Fg)
  • Electrical Force (FE)
  • Magnetic Force (Fm)
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16
Q

What are free-body diagrams used for?

A

To show the relative magnitude and direction of all forces acting on an object.

Free-body diagrams help visualize the forces in physics problems.

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17
Q

Fill in the blank: Free-body diagrams illustrate the _______ and direction of forces.

A

magnitude

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18
Q 
A book is at rest on a table top.

Create a free-body diagram to show the forces acting on the book.

A
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19
Q

What is normal force?

A

The force that surfaces exert to prevent solid objects from passing through each other

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20
Q 
A force is applied to the right to drag a sled across loosely packed snow with a rightward acceleration.

Create a free-body diagram showing the forces involved.

A
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21
Q 
A flying squirrel is gliding (no wing flaps) from a tree to the ground at constant velocity. Consider air resistance.

What would a free-body diagram for this situation look like?

A

Gravity pulls down on the squirrel while air resistance keeps the squirrel in the air for a while. Constant velocity does not mean the object is not moving.

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22
Q

What is the net force of the free-body diagram below?

A

400 N (north)

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23
Q

The force that opposes the sliding motion of two surfaces that are touching each other is called what?

A

Friction

Friction comes from the Latin word fricare meaning “to rub”

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24
Q

Friction occurs because the surface of any object is _______.

A

rough

Even surfaces that feel smooth are covered with microscopic hills and valleys

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25
Q

When two surfaces are in contact, microscopic hills and valleys of one surface stick to the tiny hills and valleys of the other surface. What is this contact known as?

A

microwelds

microwelds cause friction

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26
Q

What is static friction?

A

When a force is applied to an object but does not cause the object to move

The object does not move because the force of static friction balances the force applied.

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27
Q

If static friction is occuring, what is the net force?

A

zero

The word static means “not moving.”

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28
Q

What is kinetic friction?

A

the friction between moving surfaces

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29
Q

After static friction disappears when an object starts moving, what type of fricton immediately occurs after?

A

kinetic friction (rolling or sliding)

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30
Q

The amount of kinetic friction between two surfaces depends in part on how the surfaces _____.

A

move

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31
Q

What are two types of kinetic friction?

A
  • Sliding Friction
  • Rolling Friction
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32
Q

What type of friction opposes the motion of two sliding surfaces sliding past one another?

A

sliding friction

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33
Q

Sliding friction is caused by __________ constantly breaking and forming as objects _____ past one another.

A

microwelds, slide

34
Q

Where does rolling friction occur?

A

between the bottom of a wheel and the ground

35
Q

True or false: Sliding friction is helpful when driving.

A

False

Rolling friction is helpful when driving

36
Q

What type of friction is also known as traction?

A

Rolling friction

37
Q

Is rolling friction or sliding friction easier to overcome?

A

Rolling friction

In rolling motion, only a small area of the object is in contact with the surface at any time, reducing resistance

38
Q

What are the four fundamental forces in the universe?

A
  • Electromagnetic
  • Strong nuclear force
  • Weak nuclear force
  • Gravity
39
Q

True or false: At this moment, you are exerting an attractive force on everything around you.

A

True

Even the planet Jupiter, which is millions of kilometers away, is being attracted by your gravitational force

40
Q

Define gravity.

A

an attractive force between any two objects that depends on the masses of the objects and the distance between them

41
Q

Provide the law of Universal Gravitation.

A

F = G(m1m2 / d2)

  • F = gravitational force between the objects (in Newtons)
  • G = universal gravitational constant
  • m1 and m2 = masses of the two objects (in kilograms)
  • d = distance between the centers of the two objects (in meters)
42
Q

All ________ is affected by gravity.

A

matter

43
Q

What are the two ways gravitational force can either increase or decrease?

A
  • change in mass
  • change in distance

more mass = more gravitational force
closer distance = more gravitational force

44
Q

Nathaniel’s Argument:

No matter how far apart two objects are, the gravitational force between them never completely goes to zero.

Camden’s Argument:

Wow! You are dumb as rocks. Only the objects on Earth pull eachother with gravitational force, meaning that objects far away have a gravitational attraction of zero.

Which student is correct?

A

Nathaniel

Because the gravitational force between two objects never disappears, gravity is called a long-range force

45
Q

A region of space that has a physical quantity (such as force) at every point is also called what?

A

a field

Because objects do not have to be in contact, gravity is sometimes discussed as a field

46
Q

What is the strength of the gravitational field near Earth’s surface?

A

9.8 N/kg

47
Q

Define weight.

A

The gravitational force exerted on an object

The symbol for weight is Fg

48
Q

True or false: The weight of an object on Earth is equal to the force of Earth’s gravity on the object.

A

True

The weight of an object is exactly the gravitational force Earth exerts on the object.

49
Q

Provide the equation for weight.

A

weight (N) = mass (kg) x gravitational strength (N/kg)

The weight of an object usually is the gravitational force between the object and Earth

50
Q

True or false: Weight and mass are the same.

A

False

Weight is a force while mass is a measure of the amount of matter an object contains

51
Q

As mass increases, so does ______.

A

weight

52
Q

Define Newton’s first law of motion.

A

An object moving at a constant velocity keeps moving at that velocity unless an unbalanced net force acts on it

53
Q

What is the tendency of an object to resist any change in its motion?

A

inertia

An object will keep moving at the same speed and in the same direction unless an unbalanced force acts on it.

54
Q

What is Newton’s First Law of Motion sometimes called?

A

the law of inertia

55
Q

Define Newton’s second law of motion.

A

The acceleration of an object (which can be calculated from a specific equation) is in the same direction as the net force on the object

56
Q

Provide the Second Law of Motion equation.

A

a = Fnet / m

  1. acceleration = meters per second2
  2. net force = in newtons
  3. mass = in kilograms
57
Q

Define Newton’s third law of motion.

A

When one object exerts a force on a second object, the second one exerts a force on the first that is equal in strength and opposite in direction

These forces are sometimes called the action and reaction forces

58
Q

In a car crash, any passenger not wearing a seatbelt continues to move forward at the same speed the car was traveling? What is this due to?

A

inertia

59
Q

What describes the fall of an object on which only the force of gravity is acting?

A

free fall

60
Q

The acceleration of a falling object (in free fall) is given the symbol __ and is sometimes called the acceleration of _______.

A

g, gravity

61
Q

Define air resistance.

A

A friction-like force that opposes the motion of objects that move through the air

62
Q

What three things does air resistance depend on?

A
  • Size
  • Shape
  • Speed

of an object

63
Q

The reason why some objects fall slower than others is due to which force?

A

air resistance

64
Q

The highest speed a falling object will reach is also known as what?

A

terminal velocity

65
Q

As an object falls, the downward force of _______ causes the object to accelerate. However, as an object falls faster, the upward force of ____________ increases, which causes the ___ force on a sky diver to eventually reach zero.

A

gravity, air resistance, net

66
Q

True or false: If the net force on an object is zero, so is the object’s acceleration.

A

True

67
Q

The motion of an object when gravity is the only force acting on it is also called what?

A

free fall

In free fall, the object accelerates downward at a constant rate (9.8 m/s2 if the object was near earth’s surface)

68
Q

The sensation when there is no support force acting on your body, making you feel as though you have no weight is also known as what?

A

weightlessness

Weightlessness occurs in situations such as free falling

69
Q

List two examples of situations where freefalling takes place.

A
  • Astronauts orbiting Earth in a space station
  • A vaccum chamber experiment

1 - The spacecraft and astronauts are in free fall around Earth, creating the sensation of weightlessness

2 - Objects like a feather and a bowling ball dropped inside a vaccum chamber fall freely without air resistance

70
Q

The momentum of an object doesn’t change unless its ____, _______, or both change.

A

mass, velocity

71
Q

True or false: Momentum can be transferred from one object to another.

A

True

72
Q

What does the law of conservation of momentum state?

A

If a group of objects exert forces only on each other, their total momentum doesn’t change

73
Q

True or false: In orbit, the weight of astronauts becomes zero.

A

False

In orbit, the weight of astronauts is about 90 percent of what it would be on Earth’s surface. It decreases, but does not become zero.

74
Q

A rocket lifting up after firing its thruster is an example of…

A

action and reaction forces

75
Q

What force is necessary to move an object with a mass of 10kg at a rate of 47 m/s2?

A

470 N

76
Q

What causes some objects to fall slower than others?

A

air resistance

77
Q

What keeps the satellite moving in a circular orbit?

A

gravity

78
Q

What is the net force on a sky diver falling with a constant velocity of 10 m/s downward?

A

0N because the acceleration is 0 at a constant velocity

79
Q 
An applied force of 20N is used to accelerate an object to the right across a frictional surface. The object encounters 8N of friction. Use the diagram to determine the normal force, the net force, the coefficient of friction ("mu") between the objects and the surface, the mass, and the acceleration of the object. Neglect air resistance

m = ____________
a = _____________
Fnet = _____________
µ = ______________
FN = ___________

A

m = 31.63 kg
a = 0.38 m/s2
Fnet = 12 N
µ = 0.03
FN = 310 N

80
Q 
A rightward force is applied to a 621-g object to move it across a rough surface at constant velocity. The coefficient of friction between the object and the surface is 0.088. Use the diagram to determine the gravitational force, normal force, applied force, frictional force, and the net force. (Neglect air resistance).

m = ___________
a = ___________
Fnet = ___________
µ = ___________
Fg = ___________
FN = ___________
Fapp = ___________
Ffriction = ___________

A

m = 0.621 kg
a = 0 m/s2
Fnet = 0 N
µ = 0.088
Fg = 6.09 N
FN = 6.09 N
Fapp = 0.54 N
Ffriction = 0.54 N

CPS ADV. - McQuaid (4 decks)

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