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8th Grade > Forces > Flashcards

Forces Flashcards

1
Q

What do we need to use to know if an object is in motion?

A

A reference point

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2
Q

Reference Point

A

An object that is not moving to determine if an object is moving

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3
Q

What is a force?

A

A push or pull

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4
Q

The SI Unit for force

A

Newtons

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5
Q

How many newtons are balanced forces?

A

0N

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5
Q

Net Force

A

The total or final force

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6
Q

What is the formula for speed?

A

Distance/time

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7
Q

The faster the object the _____ the line

A

Steeper

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8
Q

What does a horizontal line on a graph mean?

A

The object not moving, the slope is 0.

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9
Q

What does SI Stand for?

A

System International

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10
Q

The SI unit for speed

A

Meters per second

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11
Q

Instantaneous Speed

A

The rate something is moving at a given instant

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12
Q

Velocity

A

Speed and direction

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13
Q

Acceleration

A

Increasing speed, decreasing speed, and changing direction

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14
Q

What two factors does the strength of friction depend on?

A

How hard the surfaces push each other & the types of surfaces

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15
Q

Mass

A

The amount of matter in an object

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16
Q

Weight

A

The force of gravity on an object at the surface of planet

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17
Q

What two factors affect the gravitational attraction of two objects?

A

Mass and distance

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18
Q

Terminal Velocity

A

The greatest velocity that can be reached by an object in free fall.

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19
Q

Air resistance

A

The type of fluid friction that acts on objects as they move through a fluid

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20
Q

Friction

A

A force that opposes motion when two objects are in contact

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21
Q

Why are units of measurement used?

A

To describe an objects motion

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22
Q

Rate

A

The amount of something that occurs or changes in one unit of time

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23
Q

How do you find the speed for an object that’s not moving at a constant speed?

A

Find the average speed

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24
Q

How do you find the average speed?

A

Divide the total distance traveled by the total time

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25
Q

What is the formula for force?

A

F = Mass x Acceleration

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26
Q

What is the basic SI unit of length

A

Meters

27
Q

What does the prefix “milli-“ mean?

A

One thousandth of the basic unit

28
Q

How are Forces described?

A

How strong they are and in which direction they act

29
Q

What part of forces are measured?

A

Its strength

30
Q

How is the strength of a force measured?

A

Using the SI unit the newton

31
Q

How is the Net Force found?

A

By combining all of the forces acting on the object

32
Q

What kind of forces have a net force?

A

Unbalanced forces

33
Q

What will unbalanced forces acting on an object do?

A

They can cause an object to start moving, stop moving, or change direction.

34
Q

How do balanced forces affect an object’s motion?

A

It will not change the objects motion

34
Q

What is the net force of a balanced object’s motion

A

0N

34
Q

What are equal forces acting in opposite directions called?

A

Balanced forces

35
Q

Friction

A

The force that two surfaces exert on each other when they rub against each other

35
Q

Which direction does friction act?

A

Opposite of the object, so it causes it to come to a stop

35
Q

Static friction

A

Acts on objects that aren’t moving

36
Q

Sliding friction

A

occurs when solid surfaces slide over each other

37
Q

Rolling friction

A

occurs when an object rolls over a surface

38
Q

Fluid friction

A

Results when an object moves through a fluid - liquid or gas

39
Q

What kind of friction needs the most force to overcome?

A

The force needed to overcome rolling friction or fluid friction is usually less than sliding friction

40
Q

Free fall

A

When the force of gravity is an unbalanced force that causes an object to accelerate

41
Q

What is acceleration near Earth’s surface due to gravity?

A

9.8m/s^2

42
Q

What type of fluid friction is objects falling through air?

A

Air resistance

43
Q

Is air resistance the same for all objects?

A

No

44
Q

What makes air resistance bigger/smaller?

A

It increases with surface area and velocity

45
Q

When does the velocity of a falling object stop increasing?

A

Once all forces are balanced. Air resistance increases until it’s equal to the force of gravity

46
Q

Projectile

A

An object that is thrown.

47
Q

Which way does a projectile move?

A

Horizontally, the force of gravity pulls it towards Earth

48
Q

Who created the three laws of motion?

A

The English mathematician Sir Isaac Newton

49
Q

What is the first law of motion?

A

The law of inertia

50
Q

Inertia

A

An object’s resistance to a change in motion

51
Q

What does the amount of inertia an object has depend on?

A

The more mass the more inertia there is, because they require a greater force to cause a change in motion

52
Q

What does Newton’s second law of motion say?

A

Acceleration depends on the object’s mass and the net force acting on the object

53
Q

What is the acceleration equation?

A

Acceleration = Net force/mass

54
Q

How is acceleration measured?

A

Meters per second (m/s^2)

55
Q

How do you increase acceleration?

A

By increasing the force. They both get larger. Also by decreasing mass

56
Q

Forces are not ____

A

One-sided

57
Q

What happens when an object exerts a force on another object?

A

The second object exerts a force back on the first object

58
Q

What are the two forces called?

A

Action and reaction

59
Q

What does Newton’s third law of motion say?

A

If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object

60
Q

Can the action and reaction be added together?

A

No, forces can only be added together if they are acting on the same object

8th Grade (13 decks)

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