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8th Grade Science > Physics > Flashcards

Flashcards in Physics Deck (107):
1

Motion

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

2

Speed

the rate of change in motion

3

Average Speed

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

4

How is speed calculated?

speed = total distance / total time
distance = meters
time = seconds

5

Force

a push or pull exerted by one object on another

5

What is force measured in?

Newtons

6

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

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

7

Net Force

the combination of all the forces acting on an object

8

Forces in the same direction...

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

9

Forces in different directions...

are subtracted

10

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

0 N

11

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

It will not change it's motion.

12

Balanced Forces: An object not moving...

will not start moving

13

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

Not 0 N

14

Unbalanced Forces: They will produce a change in...

motion (change in speed or direction)

15

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

Inertia

16

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

Equilibrium

17

Newton's First Law of Motion
(aka the Law of Inertia)

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

18

Newton's Second Law of Motion

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

19

Newton's Third Law of Motion

For every action, there is an equal and opposite reaction

21

Work is done when...

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

22

Are work and force the same?

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

23

When is work done?

when the object moves in the direction of the force

24

How is work calculated?

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

25

Power

the rate at which energy is transferred

26

How is power calculated and what is it measured in?

measured in watts (W)
power = work / time

27

Energy

the ability to do work
it is expressed in units of joules (J)

28

Kinetic Energy (KE)

the energy of motion

29

What has kinetic energy?

all moving objects

30

What determines the amount of KE an object has?

how fast it is moving & how much mass it has

31

How do you calculate kinetic energy?

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

32

Potential Energy (PE)

the energy of position

33

What is a type of potential energy?

gravitational potential energy

34

What determines the amount of gravitational PE an object has?

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

35

How do you calculate gravitational potential energy?

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

36

Mechanical Energy

the total energy of motion & position of an object

37

What are kinds of mechanical energy?

both kinetic energy & potential energy

38

Mechanical energy can be...

all KE, all PE, or some of each

39

How do you calculate mechanical energy?

mechanical energy = PE + KE

40

What is "the period of a pendulum"?

the time it takes to complete one back and forth swing

41

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

by the random movement of particles. it is kinetic

42

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

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

43

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

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

44

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

caused by an object's vibrations. it is kinetic

45

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

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

46

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

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

47

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

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

48

What is a "closed system"?

a group of objects that transfer energy only to each other

49

What is a Nonrenewable Energy Source?

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

What are the Nonrenewable Energy Sources?

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

51

What state of matter are the nonrenewable sources?

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

52

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

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

53

What is a Renewable Energy Source?

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

What are the Renewable Energy Sources?

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

55

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

13%

56

Why don't we use more renewable energy?

- 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

What is an "energy resource"?

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

58

Advantages of Fossil Fuels

• 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

Disadvantages of Fossil Fuels

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

60

Advantages of Nuclear Energy

• is a very concentrated form of energy
• does not produce air pollution

61

Disadvantages of Nuclear Energy

• produces radioactive waste
• is nonrenewable

62

Advantages of Solar Energy

• is an almost limitless source of energy
• does not produce pollution

63

Disadvantages of Solar Energy

• is expensive to use for large-scale energy production
• is practical only in sunny areas

64

Advantages of Hydropower Energy

• is renewable
• does not produce air pollution

65

Disadvantages of Hydropower Energy

• requires dams, which disrupt a river's ecosystem
• is available only where there are rivers

66

Advantages of Wind Energy

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

67

Disadvantages of Wind Energy

• is practical only in windy areas

68

Advantages of Geothermal Energy

• is an almost limitless source of energy
• power plants require little land

69

Disadvantages of Geothermal Energy

• is practical only in areas near hot spots
• produces wastewater, which can damage soil

70

Advantages of Biomass Energy

• is renewable
• is inexpensive

71

Disadvantages of Biomass Energy

• requires large areas of farmland
• produces smoke

72

What are Simple Machines?

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

73

What do Simple Machines do?

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

74

The work DONE ON a machine is called the ___

work input

75

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

input force

76

The work a machine does is CAUSED by the ___

output force

77

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

work output

78

What is Mechanical Advantage?

the benefit gained by using machines

79

A good machine puts out ___ than is ___!

1) more force
2) put into it

80

Types of Simple Machines: What are Gears?

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

81

examples of Gears

clock, bicycle gear chains, drill

82

Types of Simple Machines: What is an Inclined Plane?

a sloping surface such as a ramp

83

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

effort & distance

84

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

longer

85

examples of Inclined Planes

staircase, ramp

86

Types of Simple Machines: What is a Lever?

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

87

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

weight

88

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

1) lever
2) upward
3) opposite

89

examples of Levers

door on hinges, seesaw, hammer, bottle opener

90

Types of Simple Machines: What is a Pulley?

a wheel that usually has a groove around the outside edge

91

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

rope or belt

92

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

1) down
2) lift
3) attached

93

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

1) easier
2) gravity

94

examples of Pulleys

flagpole, ski lift

95

Types of Simple Machines: What is a Screw?

an INCLINED PLANE wrapped around a shaft or cylinder

96

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

1) move
2) rotated

97

examples of Screws

bolt, jar lid

98

Types of Simple Machines: What is a Wedge?

2 inclined planes joined back to back

99

Wedges are used to ___ things.

split

100

examples of Wedges

axe, zipper, knife

101

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

consists of 2 wheels of different sizes that rotate together

102

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

1) small
2) larger
3) less

103

examples of the Wheel & Axle

door knob, car/wagon wheels

104

Types of Simple Machines: What are Compound Machines?

2 or more simple machines working together to make work easier

105

examples of Compound Machines

wheelbarrow, can opener, stapler

106

What is Mechanical Advantage?

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

107

What is the formula for Mechanical Advantage?

Mechanical Advantage = Output Force / Input Force