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Flashcards in Topic 2 Deck (78):
1

When will a body move in a circular path

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

2

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

Changing velocity

3

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

Centripetal force

4

What are the four main centripetal forces

Gravitational
Frictional
Tension
Electrostatic

5

Example of gravitational force

Orbiting satellite

6

Example of frictional force

Car on a roundabout

7

Example of tension force

Hammer thrower

8

Example of electrostatic force

Electron orbiting the nucleus

9

Equation for momentum

Momentum = mass x velocity

Kg m/s. Kg. M/s

P = m x v

10

Equation for force not needed to remember

Change in momentum / time taken for the change

F = mv - mu/ t


11

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

Are also large this can be v dangerous

12

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

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

13

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...

Needed is reduced

14

What does Newton’s third law relate to

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

15

What does Newton’s third law state

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

The action force and the reaction force act on different bodies

16

In Newton’s third law the reactants have to be

Reacting on different bodies

17

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...

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

18

What is human reaction time

The time between a stimulus occurring and a response.

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

19

What’s a typical human reaction time

Between 0.2 s and 0.25 s

20

What can affect reaction time of humans

Tiredness
Alcoholic and drugs
Distractions
Age

21

How can you determine human reaction time

Using the ruler drop test

22

Equation for reaction time

= √ 2 x distance ruler falls/gravity

23

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

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

24

What is stopping distance

The total distance over which a vehicle comes to rest

25

Equation for stopping distance

= thinking distance + braking distance

26

What’s thinking distance

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

27

What’s braking distance

The distance the car travels while it is slowing down

28

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

They increase

29

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

It doubles

30

What factor does the breaking distance increase by?

4

31

Thinking distance increases when:

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

32

Braking distance increases when

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

Thinking distance is what to the speed?

Directly proportional

34

Braking distance is proportional to

(Speed)^2

35

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

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

36

What are the eight main energy stores

Chemical
Kinetic
Gravitational potential
Elastic
Thermal
Magnetic
Electrostatic
Nuclear

37

Example of chemical energy store

Fuel
Food
Battery

38

Example of kinetic energy store

Moving objects

39

Example of gravitational potential energy store

Raised mass

40

Example of elastic energy store

Stretched spring

41

Example of thermal snergy store

Hot object

42

Example of magnetic energy store

Two magnets

43

Example of electrostatic energy store

Two charges

44

Example of nuclear energy store

Radioactive decay

45

What’s a closed system

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

Eg pan with lid on

46

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

There is no net change

47

What are the four ways that energy can be transferred

Mechanically
Electrically
Thermally
Radiation

48

How is energy transferred mechanically

By a force moving through a distance

49

How is energy transferred electrically

By the use of electric current

50

How is energy transferred thermally

Because of a difference in temperature

51

How is energy transferred by radiation

By waves such as electromagnetic or sound

52

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

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

Thickness of walls

Material walls are made from

53

How can unwanted energy transfers be reduced

By thermal insulation and lubrication

54

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

One with a lower thermal conductivity

55

Different material have different

Relative thermal conductivities

56

A verycefficient machine has an efficiency that is nearly

100%

57

Equation for efficiency

Useful energy/total energy x 100

58

Main energy resources include both

Renewable and non renewable resources

59

What are renewable energy resources

They will not run out
Most do not cause pollution or emit carbon dioxide

60

Examples of renewable energy resources

Bio-fuels
Hydroelectricity
Wind turbines
Tidal power
Solar cells

61

What are bio-fuels

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

62

What’s hydroelectricity

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

63

What are wind turbines

Use kinetic energy from the wind to generate electricity

64

What’s tidal power

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

65

What’s solar cells

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

What are non renewable resources

Are resources that will run out eventually

67

Examples of non renewable resources

Fossil fuels
Nuclear fuels

They are available all the time unlike some renewable resources

68

Fossil fuels...

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

69

Nuclear fuels...

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

70

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

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

What’s inertial mass

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

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

•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

What is most of the worlds energy

Fossil fuels

74

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

More carbon dioxide in the atmosphere

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

75

Main issues with using the earths energy supplies

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

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

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

Explain how force is related to momentum

Force is the rate of change of momentum

It’s the change in momentum divided by time taken

78

KE is proportional to

V^2