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PHYSICS > Topic 2 > Flashcards

Topic 2 Flashcards

1
Q

When will a body move in a circular path

A

If it’s motion is at right angles to a force that acts inwards along the radius of path

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2
Q

A body moving in a circular part with constant speed still has a?…

A

Changing velocity

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3
Q

What’s the force acting in words along the radius of the circle called

A

Centripetal force

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4
Q

What are the four main centripetal forces

A

Gravitational
Frictional
Tension
Electrostatic

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5
Q

Example of gravitational force

A

Orbiting satellite

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6
Q

Example of frictional force

A

Car on a roundabout

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7
Q

Example of tension force

A

Hammer thrower

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8
Q

Example of electrostatic force

A

Electron orbiting the nucleus

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9
Q

Equation for momentum

A

Momentum = mass x velocity

Kg m/s. Kg. M/s

P = m x v

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10
Q

Equation for force not needed to remember

A

Change in momentum / time taken for the change

F = mv - mu/ t

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11
Q

When the mass or the deceleration of a vehicle are large, the Forbes exerted on the passengers…

A

Are also large this can be v dangerous

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12
Q

Car safety features such as seat belts and crumple zones do what?

A

Revise the size of the forces on the driver and pssengers by increasing the time over which the vehicle comes to rest

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13
Q

Changing the time changes the force needed to change the momentum. By increasing the time over which the change in momentum takes place… the force…

A

Needed is reduced

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14
Q

What does Newton’s third law relate to

A

Bodies in equilibrium and can be applied to collisions when considering the conservation of momentum

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15
Q

What does Newton’s third law state

A

That for every action there is an equal and opposite reaction.

The action force and the reaction force act on different bodies

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16
Q

In Newton’s third law the reactants have to be

A

Reacting on different bodies

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17
Q

When a truck and car collide, they exert equal and opposite forces on each other are in contact for same amount of time. Newton’s 3rd law is obeyed.

Momentum…

A

Is conserved : the total momentum before the collisions equals the total momentum afterwards

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18
Q

What is human reaction time

A

The time between a stimulus occurring and a response.

Related to how quickly the human brain can process information and react to it

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19
Q

What’s a typical human reaction time

A

Between 0.2 s and 0.25 s

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20
Q

What can affect reaction time of humans

A

Tiredness
Alcoholic and drugs
Distractions
Age

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21
Q

How can you determine human reaction time

A

Using the ruler drop test

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22
Q

Equation for reaction time

A

= √ 2 x distance ruler falls/gravity

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23
Q

Explain why the reaction time doubled when the distance that a ruler falls increases by a factor or 4

A

Reaction time Is proportional to the square root of the distance an object falls. The square foot of 4 is 2 so four times the distance means twice the reaction time

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24
Q

What is stopping distance

A

The total distance over which a vehicle comes to rest

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25
Q

Equation for stopping distance

A

= thinking distance + braking distance

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26
Q

What’s thinking distance

A

The distance the car travels while the driver reacts to the danger and applies the brakes

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27
Q

What’s braking distance

A

The distance the car travels while it is slowing down

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28
Q

What happens to thinking and braking distance when the cars speed increases?

A

They increase

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29
Q

When you double the speed of the car what happens to the thinking distance ?

A

It doubles

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30
Q

What factor does the breaking distance increase by?

A

4

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31
Q

Thinking distance increases when:

A

The driver is tired
The driver is distracted
The driver has taken alcohol or drugs

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32
Q

Braking distance increases when

A

The amount of friction between the tyre and road decreases
To road is icy or wet
The brakes or tyres are worn
The mass of the car is bigger

33
Q

Thinking distance is what to the speed?

A

Directly proportional

34
Q

Braking distance is proportional to

A

(Speed)^2

35
Q

What’s the equation that governs a force applied to the brakes, the kinetic energy is transferred to thermal energy and the vehicle comes to rest over a certain distance

A

F x d = 1/2 x m x v^2

36
Q

What are the eight main energy stores

A 
Chemical 
Kinetic
Gravitational potential
Elastic 
Thermal
Magnetic
Electrostatic
Nuclear
37
Q

Example of chemical energy store

A

Fuel
Food
Battery

38
Q

Example of kinetic energy store

A

Moving objects

39
Q

Example of gravitational potential energy store

A

Raised mass

40
Q

Example of elastic energy store

A

Stretched spring

41
Q

Example of thermal snergy store

A

Hot object

42
Q

Example of magnetic energy store

A

Two magnets

43
Q

Example of electrostatic energy store

A

Two charges

44
Q

Example of nuclear energy store

A

Radioactive decay

45
Q

What’s a closed system

A

One where energy can flow in or out of the system but there is no transfer of mass

Eg pan with lid on

46
Q

What happens to the net change in an a nervy transfer in a closed system

A

There is no net change

47
Q

What are the four ways that energy can be transferred

A

Mechanically
Electrically
Thermally
Radiation

48
Q

How is energy transferred mechanically

A

By a force moving through a distance

49
Q

How is energy transferred electrically

A

By the use of electric current

50
Q

How is energy transferred thermally

A

Because of a difference in temperature

51
Q

How is energy transferred by radiation

A

By waves such as electromagnetic or sound

52
Q

The rate at which thermal energy is transferred through a wall of a house depends on :

A

The difference in temperature between the warmer interior and the colder exterior

Thickness of walls

Material walls are made from

53
Q

How can unwanted energy transfers be reduced

A

By thermal insulation and lubrication

54
Q

A material with high thermal conductivity is a better conductor of energy than

A

One with a lower thermal conductivity

55
Q

Different material have different

A

Relative thermal conductivities

56
Q

A verycefficient machine has an efficiency that is nearly

A

100%

57
Q

Equation for efficiency

A

Useful energy/total energy x 100

58
Q

Main energy resources include both

A

Renewable and non renewable resources

59
Q

What are renewable energy resources

A

They will not run out

Most do not cause pollution or emit carbon dioxide

60
Q

Examples of renewable energy resources

A 
Bio-fuels
Hydroelectricity
Wind turbines 
Tidal power
Solar cells
61
Q

What are bio-fuels

A

Animal or plant matter used to produce thermal energy, electrical energy or used to power cars

62
Q

What’s hydroelectricity

A

Generated electricity from water behind a dam flowing down a pipe and turning a turbine to generate electricity

63
Q

What are wind turbines

A

Use kinetic energy from the wind to generate electricity

64
Q

What’s tidal power

A

Used the rise and fall of the tide or tidal currents to generate electricity

65
Q

What’s solar cells

A

Convert solar energy, or energy from the sun, directly to electricity. Solar energy can also be used directly to cook food or heat water

66
Q

What are non renewable resources

A

Are resources that will run out eventually

67
Q

Examples of non renewable resources

A

Fossil fuels
Nuclear fuels

They are available all the time unlike some renewable resources

68
Q

Fossil fuels…

A 
Are coal, oil and natural gas 
They are used: 
To generate electricity
To power transport
To hear homes and for cooking
69
Q

Nuclear fuels…

A

Such as uranium are used:
To generate electricity
As energy sources in spacecraft

70
Q

Describe how different renewable and non-renewable resources are used for transport

A

Renewable and non-renewable energy resources can both be used in power stations, leading to the production of electricity which is used to power trains. Electrical energy can also be supplied from other renewable sources such as solar, hydroelectric and wind

Biofuel in the form of methanol is an example of how renewable fuel can be used to power cars and solar power is also being developed to do more of this. Petrol and diesel, from oil, are examples of non- renewable fuels that are used to power cars

71
Q

What’s inertial mass

A

A measure of how difficult it is to change the velocity of an object (including from at rest) and know that it is defined as the ratio of force over acceleration

72
Q

What are the factors which have caused the use of energy resources changing over the years

A

•The worlds population
-in the last 200 years pop went from 1 bill to 7 bill-

•the development of technically
-cars trains and planes and other devices have increased in number and all require energy-

• electrical energy
-power stations require fuels in order to generate electricity-

73
Q

What is most of the worlds energy

A

Fossil fuels

74
Q

Fossil fuels are a finite reserve so will run out and not be replaced. Greater use of fossil fuels will lead too…?

A

More carbon dioxide in the atmosphere

There will be greater global warming leading to severe weather flooding and threats to food supplies

75
Q

Main issues with using the earths energy supplies

A

Threats to food supplies to those who need them
Global warming and floods due to using fossil fuels
Running out of non renewable resources

76
Q

Wood is a biofuel. Suggest why wood had been used constantly for many years whereas other fuels have only been used much more recently

A

Wood has been readily available for thousands of years and has not had to be discovered, minds or have any extra technology developed in order for it to be used to produce thermal energy

77
Q

Explain how force is related to momentum

A

Force is the rate of change of momentum

It’s the change in momentum divided by time taken

78
Q

KE is proportional to

A

V^2

PHYSICS (10 decks)

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