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8th Grade Science > Physics > Flashcards

Physics Flashcards

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1
Q

Motion

A

an object changing position over time, relative to a reference point

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2
Q

Speed

A

the rate of change in motion

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3
Q

Average Speed

A

the distance traveled by an object divided by the time taken to go the distance

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4
Q

How is speed calculated?

A 
speed = total distance / total time
distance = meters
time = seconds
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5
Q

Force

A

a push or pull exerted by one object on another

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5
Q

What is force measured in?

A

Newtons

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6
Q

Will motion always occur when a force acts on an object?

A

No (push on a wall; wall doesn’t move)

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7
Q

Net Force

A

the combination of all the forces acting on an object

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8
Q

Forces in the same direction…

A

help us move objects; are added to create a net force

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9
Q

Forces in different directions…

A

are subtracted

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10
Q

Balanced Forces: What will the net force on an object be?

A

0 N

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11
Q

Balanced Forces: What will a moving object do when balanced?

A

It will not change it’s motion.

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12
Q

Balanced Forces: An object not moving…

A

will not start moving

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13
Q

Unbalanced Forces: What will the net force on an object be?

A

Not 0 N

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14
Q

Unbalanced Forces: They will produce a change in…

A

motion (change in speed or direction)

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15
Q

Definition = the tendency of an object to resist changes in its state of motion

A

Inertia

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16
Q

Definition = when all the forces acting upon an object balance each other, the object will be in this state

A

Equilibrium

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17
Q

Newton’s First Law of Motion

aka the Law of Inertia

A

An object in motion will stay in motion, and an object at rest will stay at rest, until acted upon by an outside and unbalanced force

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18
Q

Newton’s Second Law of Motion

A

A net force acting on an object causes the object to accelerate in the direction of the force. The amount of acceleration is determined by the mass of the object & size of the force

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19
Q

Newton’s Third Law of Motion

A

For every action, there is an equal and opposite reaction

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21
Q

Work is done when…

A

a force causes an object to move in the direction of the force

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22
Q

Are work and force the same?

A

No - just because you apply force does not mean work was done

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23
Q

When is work done?

A

when the object moves in the direction of the force

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24
Q

How is work calculated?

A

work = force x distance
force (f) = Newtons
distance (d) = meters
work = joules (J)

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25
Q

Power

A

the rate at which energy is transferred

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26
Q

How is power calculated and what is it measured in?

A

measured in watts (W)

power = work / time

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27
Q

Energy

A

the ability to do work

it is expressed in units of joules (J)

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28
Q

Kinetic Energy (KE)

A

the energy of motion

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29
Q

What has kinetic energy?

A

all moving objects

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30
Q

What determines the amount of KE an object has?

A

how fast it is moving & how much mass it has

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31
Q

How do you calculate kinetic energy?

A

KE = (mv^2) / 2
(mass x velocity squared) / 2
m = mass
v = velocity/speed

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32
Q

Potential Energy (PE)

A

the energy of position

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33
Q

What is a type of potential energy?

A

gravitational potential energy

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34
Q

What determines the amount of gravitational PE an object has?

A

its weight and its height (how far it has to fall)

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35
Q

How do you calculate gravitational potential energy?

A

gravitational PE = weight x height
weight = Newtons (N)
height = meters (m)

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36
Q

Mechanical Energy

A

the total energy of motion & position of an object

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37
Q

What are kinds of mechanical energy?

A

both kinetic energy & potential energy

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38
Q

Mechanical energy can be…

A

all KE, all PE, or some of each

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39
Q

How do you calculate mechanical energy?

A

mechanical energy = PE + KE

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40
Q

What is “the period of a pendulum”?

A

the time it takes to complete one back and forth swing

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41
Q

How is Thermal Energy formed? Is it Potential or Kinetic?

A

by the random movement of particles. it is kinetic

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42
Q

How is Chemical Energy formed? Is it Potential or Kinetic?

A

by the energy of a compound as its atoms are rearranged. it is potential, then kinetic

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43
Q

How is Electrical Energy formed? Is it Potential or Kinetic?

A

by the energy of moving electrons. it is potential, then kinetic

44
Q

How is Sound Energy formed? Is it Potential or Kinetic?

A

caused by an object’s vibrations. it is kinetic

45
Q

How is Light Energy formed? Is it Potential or Kinetic?

A

produced by the vibrations of electronically charged particles. it is kinetic

46
Q

How is Nuclear Energy formed? Is it Potential or Kinetic?

A

caused by changes in the nucleus of an atom. it is potential, then kinetic

47
Q

How is Mechanical Energy formed? Is it Potential or Kinetic?

A

by the KE and PE of an object. it is both kinetic and potential

48
Q

What is a “closed system”?

A

a group of objects that transfer energy only to each other

49
Q

What is a Nonrenewable Energy Source?

A

an energy resource that cannot be replaced or is replaced much more slowly than it is used. it cannot be made again in a short period of time

50
Q

What are the Nonrenewable Energy Sources?

A
  1. Coal
  2. Oil (Petroleum)
  3. Natural Gas
  4. Uranium
51
Q

What state of matter are the nonrenewable sources?

A

Crude Oil (Petroleum) - liquid
Natural Gas / Propane - gas
Coal - solid
Uranium Ore - solid

52
Q

Why are coal, petroleum, natural gas, and propane considered fossil fuels?

A

they were formed from the buried remains (fossils) of plants & animals that lived millions of years ago

53
Q

What is a Renewable Energy Source?

A

an energy source that is naturally replaced more quickly than it is used. it can be replenished naturally in a short period of time

54
Q

What are the Renewable Energy Sources?

A
  1. Biomass (trash, trees, etc.)
  2. Hydropower (water)
  3. Geothermal
  4. Solar
  5. Wind
55
Q

In 2011, what % of U.S. electricity was generated from renewable sources?

A

13%

56
Q

Why don’t we use more renewable energy?

A
  • more expensive to produce & use
  • resources are in remote areas so it is a challenge to build power lines to cities
  • they are not always available (cloudy days, calm days, drought)
  • safety concerns regarding nuclear failure
57
Q

What is an “energy resource”?

A

a natural resource that can be converted into other forms of energy to do work

58
Q

Advantages of Fossil Fuels

A
  • provide a large amount of thermal energy per unit of mass
  • are easy to get & transport
  • can be used to generate electricity & to make products such as plastic
59
Q

Disadvantages of Fossil Fuels

A
  • are nonrenewable
  • produce smog
  • release substances that can cause acid precipitation
  • create a risk of oil spills
60
Q

Advantages of Nuclear Energy

A
  • is a very concentrated form of energy

* does not produce air pollution

61
Q

Disadvantages of Nuclear Energy

A
  • produces radioactive waste

* is nonrenewable

62
Q

Advantages of Solar Energy

A
  • is an almost limitless source of energy

* does not produce pollution

63
Q

Disadvantages of Solar Energy

A
  • is expensive to use for large-scale energy production

* is practical only in sunny areas

64
Q

Advantages of Hydropower Energy

A
  • is renewable

* does not produce air pollution

65
Q

Disadvantages of Hydropower Energy

A
  • requires dams, which disrupt a river’s ecosystem

* is available only where there are rivers

66
Q

Advantages of Wind Energy

A
  • is renewable
  • is relatively inexpensive to generate
  • does not produce air pollution
67
Q

Disadvantages of Wind Energy

A

• is practical only in windy areas

68
Q

Advantages of Geothermal Energy

A
  • is an almost limitless source of energy

* power plants require little land

69
Q

Disadvantages of Geothermal Energy

A
  • is practical only in areas near hot spots

* produces wastewater, which can damage soil

70
Q

Advantages of Biomass Energy

A
  • is renewable

* is inexpensive

71
Q

Disadvantages of Biomass Energy

A
  • requires large areas of farmland

* produces smoke

72
Q

What are Simple Machines?

A

a simple machine is a machine with few or no moving parts.

73
Q

What do Simple Machines do?

A

simple machines make work easier (work is done when a force is applied through a distance)

74
Q

The work DONE ON a machine is called the ___

A

work input

75
Q

The work DONE ON a machine is called the work input, and this work is caused by an ___

A

input force

76
Q

The work a machine does is CAUSED by the ___

A

output force

77
Q

The work a machine does is CAUSED by the output force and is called ___

A

work output

78
Q

What is Mechanical Advantage?

A

the benefit gained by using machines

79
Q

A good machine puts out ___ than is ___!

A

1) more force

2) put into it

80
Q

Types of Simple Machines: What are Gears?

A

two toothed wheels that fit together either directly or through a chain or belt

81
Q

examples of Gears

A

clock, bicycle gear chains, drill

82
Q

Types of Simple Machines: What is an Inclined Plane?

A

a sloping surface such as a ramp

83
Q

An inclined plane can alter the ___ and ___ involved in doing work.

A

effort & distance

84
Q

The trade-off of an inclined plane is that an object must be moved a ___ distance than if lifted straight up.

A

longer

85
Q

examples of Inclined Planes

A

staircase, ramp

86
Q

Types of Simple Machines: What is a Lever?

A

a straight rod or board that pivots a point known as a fulcrum

87
Q

A fulcrum can be moved depending on the ___ of the object.

A

weight

88
Q

Pushing down on one end of the ___ results in the ___ motion of the ___ end of the fulcrum.

A

1) lever
2) upward
3) opposite

89
Q

examples of Levers

A

door on hinges, seesaw, hammer, bottle opener

90
Q

Types of Simple Machines: What is a Pulley?

A

a wheel that usually has a groove around the outside edge

91
Q

The groove is for a ___ or ___ to move around the pulley.

A

rope or belt

92
Q

By pulling ___ on the rope it can ___ an object that is ___ to the rope.

A

1) down
2) lift
3) attached

93
Q

Work is made ___ because pulling down on the rope is made easier due to ___.

A

1) easier

2) gravity

94
Q

examples of Pulleys

A

flagpole, ski lift

95
Q

Types of Simple Machines: What is a Screw?

A

an INCLINED PLANE wrapped around a shaft or cylinder

96
Q

The inclined plane allows the screw to ___ itself or to move an object or material surrounding it when ___.

A

1) move

2) rotated

97
Q

examples of Screws

A

bolt, jar lid

98
Q

Types of Simple Machines: What is a Wedge?

A

2 inclined planes joined back to back

99
Q

Wedges are used to ___ things.

A

split

100
Q

examples of Wedges

A

axe, zipper, knife

101
Q

Types of Simple Machines: What is a Wheel and Axle?

A

consists of 2 wheels of different sizes that rotate together

102
Q

When the ___ wheel (axle) is turned the ___ wheel moves a greater distance, and ___ force is needed to move it.

A

1) small
2) larger
3) less

103
Q

examples of the Wheel & Axle

A

door knob, car/wagon wheels

104
Q

Types of Simple Machines: What are Compound Machines?

A

2 or more simple machines working together to make work easier

105
Q

examples of Compound Machines

A

wheelbarrow, can opener, stapler

106
Q

What is Mechanical Advantage?

A

the benefit gained by using machines. it compares the INPUT FORCE with the OUTPUT FORCE

107
Q

What is the formula for Mechanical Advantage?

A

Mechanical Advantage = Output Force / Input Force

8th Grade Science (7 decks)

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