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Physics > P1D- Forces, energy, work, power and pressure > Flashcards

P1D- Forces, energy, work, power and pressure Flashcards

1
Q

What is a force

A

A force is a push or pull.

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2
Q

What are forces measured in

A

Newtons (N)

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3
Q

What effects can forces have

A

pushing, pulling, bending, stretching, squeezing tearing

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4
Q

What can forces do

A

change the size of an object

change the motion of an object

change the shape of an object

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5
Q

what are some examples of Non contact forces

A

Gravity
Magnetism
Electrostatic

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6
Q

What are some examples of Contact forces

A

friction
drag (air resistance)
upthrust
tension

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7
Q

What makes a force balanced?

A

Forces are balanced when they are equal in size and opposite in direction, causing no change in motion.

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8
Q

What are electrostatic forces

A

those between charges such as electrons. Like charges repel and unlike charges attract

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9
Q

What two factors determines whether a force will cause the object will move and the direction it does so?

A

The size and directions of forces

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10
Q

whats the force that causes all the objects in the universe to attract

A

gravity

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11
Q

what is the resultant force

A

the added up force that represents the combined effect of all forces acting on an object.

e.g Twelve husky dogs are pulling a sledge. The sledge is travelling to the right and each dog is pulling with a force of 50N. There is friction with the force of 250N that is trying to slow the sledge, and there fore must be pointing to the left.

The total force to the right (12x50)= 600N

The total force to the left is 250N

The resultant force = 600-250=350 to the right. (direction needed)

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12
Q

what does zero resultant force mean

A

object is at equilibrium

no acceleration- constant speed/stationary

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13
Q

the ________ varies with the load attached to it (______)

A

extension, force

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14
Q

What is the limit of proportionality

A

the point at which the extension is no longer proportional to the load- material starts behaving unpredictably.

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15
Q

When forces are balanced they are in _________

when forces are unbalanced they are in __________

A

equilibrium

disequilibrium

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16
Q

Whats an experiment to show hooke’s law?

A
  1. assemble the apparatus: ruler, spring, stand, clamp, masses
  2. take the first mass which consists of the hook and the base blate (100g) and measure the new position of the bottom end of the spring of the ruler. The difference in the reasings is the extension of the spring
  3. add masses one by one to the first one.
  4. Calculate the extension and plot a graph of extension
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17
Q

how is the graph drawn for hooke’s law

A

force (massxgravity)- on the y axis

extension- on the x axis

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18
Q

what is a spring that obeys hookes law known to perform

A

proportional behaviour

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19
Q

equation for hooke’s law

A

force (F)= spring constant (k) x extension of spring (x)

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20
Q

what is friction

A

a force that opposes motion

e.g air resistance

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21
Q

where can friction be useful

A

bicycle wheels and bicycle brake pads

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22
Q

what do forces have to be for an objects speed or direction of movement to change

A

unbalanced

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23
Q

Newtons second law equation

A

F=ma

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24
Q

Newton’s first law

A

Objects will remain at rest or move with a constant velocity unless acted on by resultant forces

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25
Q

Newton’s second law

A

The acceleration of an object is proportional to the resultant force acting on it and inversely proportional to the objects mass (F=ma)

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26
Q

for the equation to apply what conditions must ‘force’ and ‘mass’ meet?

A

mass is constant

force is constant

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27
Q

mass should always be in ______

A

kgs/g

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28
Q

whats newtons third law

A

for every action (force) in nature there is an equal and opposite reaction.

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29
Q

what is a moment

A

the turning effect produced when a force is exerted on an object

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30
Q

Examples of moments

A

door and door hinge

see saws

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31
Q

formula for moment of a force

A

size of moment (Nm): force (N) x perpendicular distance from pivot moment (m)

Fd

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32
Q

what does it mean if an object is not turning

A

the sum of clockwise moments about any pivot equals the sum of the anticlockwise moments about the same pivot

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33
Q

what is equilibrium

A

a state of balance or stability: no resultant force no resultant moment

34
Q

what should you always include after writing the size of moment

A

clockwise/anticlockwise

35
Q

what is the centre of mass

A

the point through which the weight of an object acts

36
Q

How do you find the centre of mass of simple objects such as a piece of card

A
  1. hang up the object
  2. suspend a mass from the same place
  3. mark the position of the thread
  4. the centre of mass is somewhere along the line of the threat
  5. repear steps 1-3 with the object suspended from a different place
  6. the centre of mass is where the two lines meet
37
Q

when is an object stable

A

when its centre of gravity lies above its base

38
Q

where is the centre of gravity of a symmetrical object

A

at the point of symmetry

39
Q

when is an object considered in stable equilibrium

A

when its difficult to topple

40
Q

what is pressure

A

the ratio of force to area.

41
Q

the equation for pressure

A

p=F/A

pressure measure in pascals

force: newtons

area: m^2

42
Q

when is work done

A

when the application of a force results in movement

43
Q

what does the amount of work done depend on

A

the magnitude of the force and the distance moved in the direction of the force

44
Q

What is the equation for work done

A

Work (joules/ Nm)= Force (N) x distance moved in the direction of force (m)

45
Q

how can work done be calculated when object is lifted vertically

A

the force moved is the weight of object
distance is the height (vertical distance)

46
Q

When is more work done

A

when the mass is bigger or the object is raised further

47
Q

what is potential energy

A

stored or hidden energy

48
Q

when does a spring have elastic potential energy

A

when a spring is compressed or stretched

49
Q

what can potential energy be transferred to

A

an object and make it move so give it kinetic energy

50
Q

where can kinetic and potential energy be seen

A

energy transfers during the swing of a pendulum

at each end of its swing the pendulum has a maximum amount of gravitational potential energy and at the middle the potential energy has been transferred to kinetic.

51
Q

an object gains ___________ potential energy as it gains __________. _________ has to be done to increase the height of the object above the ground. Therefore ________ in gravitational _________ energy = _____ ______ on that object against gravity.

A

gravitational
height
work
gain
potential
work done

52
Q

formula for gravitational potential energy

A

potential energy (J) mgh -
m=mass (kg/g)
g= acceleration due to gravity
h=height (m)

53
Q

formula for kinetic energy

A

k.e (j) = 1/2mv^2

m= mass (kg/g)
v= velocity (m/s)

54
Q

what does the principle of conservation of energy state

A

energy can not be created or destroyed, it can only be transferred from one store to the other

55
Q

energy can be _________ (spread out) to the _________ by heating and ___________

A

dissipated
surroundings
radiation

56
Q

total mechanical energy formula

A

kinetic energy+ potential+ elastic

57
Q

what is power

A

work done per unit time (energy transferred per unit time)

58
Q

power formula

A

change in energy/time or work done/ time

59
Q

what is power measured in

A

watts

60
Q

what is energy efficiency

A

the ratio of the useful power or energy output from a system to its total power or energy input.

61
Q

formula for energy efficiency

A

useful energy/total energy x 100

62
Q

what should the total amount of energy transferred into the system equal to

A

the total amount of energy transferred away from the system

63
Q

What is chemical potential energy?

A

It is energy stored in chemical bonds, such as in fossil fuels like coal, oil, and natural gas.

64
Q

How is energy released from fuels?

A

Through combustion, where chemical bonds are broken, releasing heat energy.

65
Q

How do waves generate energy?

A

The movement of waves drives turbines, which convert kinetic energy into electrical energy.

66
Q

What is tidal energy?

A

Energy generated from the movement of water caused by tides, often using tidal barrages or underwater turbines.

67
Q

Name one advantage of tidal energy.

A

It is renewable and predictable.

68
Q

Name one disadvantage of wave energy

A

It can disrupt marine ecosystems and is location-dependent.

69
Q

What is geothermal energy?

A

Energy from the heat stored in the Earth’s crust.

70
Q

How is geothermal energy harnessed?

A

By using steam or hot water from underground to turn turbines and generate electricity.

71
Q

Name one advantage of geothermal energy.

A

It is renewable and produces low emissions.

72
Q

Name one disadvantage of geothermal energy.

A

It is limited to regions with geothermal activity.

73
Q

How is nuclear energy generated?

A

By splitting atoms (nuclear fission) in a reactor to release heat, which produces steam to drive turbines.

74
Q

What is one advantage of nuclear energy?

A

It produces large amounts of energy with no greenhouse gas emissions during operation.

75
Q

What is one disadvantage of nuclear energy?

A

It generates radioactive waste that needs to be safely stored.

76
Q

How is solar energy harnessed?

A

Using solar panels (photovoltaic cells) to convert sunlight into electricity or solar heaters for heat.

77
Q

Name one advantage of solar energy.

A

It is renewable and abundant in sunny areas.

78
Q

Name one disadvantage of solar energy.

A

It is weather-dependent and requires large areas for panels.

79
Q

How is wind energy generated?

A

By using wind turbines that convert the kinetic energy of moving air into electrical energy.

80
Q

What is one advantage of wind energy?

A

It is renewable and produces no greenhouse gas emissions.

81
Q

What is one disadvantage of wind energy?

A

It is intermittent and depends on wind availability.

82
Q

_________ energy -> ___________ energy

-> __________ energy

A

potential

kinetic

electrical/elastic

Physics (2 decks)

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