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science > year 2 chap 9 > Flashcards

year 2 chap 9 Flashcards

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Biology 101 flashcards
1
Q

what is a force?

A

a push and pull that acts upon an object as a result of its interaction with other objects

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2
Q

what is a push force?

A

force which you exert to move an object away from you

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3
Q

what is a pull force?

A

force which you exert to move an object towards you

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4
Q

what are contact forces?

A

forces acting between 2 objects that are in physical contact with each other

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5
Q

what are non-contact forces?

A

forces acting between two objects that are not touching each other

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6
Q

what are the two types of contact forces?

A

friction and elastic force

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7
Q

what is friction?

A

the force that opposes motion between two surfaces in contact

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8
Q

what is elastic force?

A

force acting on a stretched or compressed elastic object to return to its original shape

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9
Q

what is a real-life application of friction?

A

rock climbers use chalk to absorb moisture on their hands, which increases friction and improves their grip on the rock wall

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10
Q

what is a real-life application of elastic force?

A

climbers use climbing ropes that can stretch and exert elastic force, when the climber falls, the rope stretches and the elastic force exerted increases, this reduces the impact felt by the climber when they fall

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11
Q

what are the two types on non-contact forces?

A

gravitational force and magnetic force

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12
Q

what is gravitational force?

A

the force that attracts two objects towards each other

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13
Q

what is magnetic force?

A

the force exerted between a magnet and another magnet or magnetic material

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14
Q

what is a real-life application of gravitational force?

A

when someone falls from the sky, they are pulled towards earth’s surface due to earth’s gravitational force

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15
Q

what is a real-life application of magnetic force?

A

every magnet has a north and south pole, when unlike poles are brought close to each other, they pull together due to the magnetic force of attraction

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16
Q

when a planet exerts gravitational force on an object and pulls it towards its centre, the object is known to have ___

A

weight

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17
Q

what an object is placed on a table, what are the two main forces acting on the object?

A
  • weight (downwards to the centre
    of Earth)
  • normal contact force (upwards
    and perpendicular to table top)
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18
Q

what is a balanced force?

A
  • net (resultant) force acting on the object equals to zero
  • object in equilibrium (balance)
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19
Q

when there is balanced force, what happens to the object in equilibrium?

A

the object remains at rest or moves with constant speed in a straight line

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20
Q

what is an unbalanced force?

A
  • net (resultant) force acting on the object does not equal to zero
  • object is not in equilibrium (balance)
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21
Q

what happens when the object is not in equilibrium?

A

it either changes speed, direction or both

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22
Q

what does “resultant” mean?

A

occurring or produced as a result of something

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23
Q

what is weight? and what is its SI unit?

A

the measurement of the gravitational force acting on an object and its SI unit is newtons (N)

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24
Q

what is mass? and what is its SI unit?

A

the amount of matter in an object and its SI unit is kilograms (kg)

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25
Q

what can be used to measure weight?

A

a spring balance or a newton meter

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26
Q

what can be used to measure mass?

A

an electronic balance or a beam balance

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27
Q

mass ___ regardless of location while weight ___ with location

A

remains constant ; may change

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28
Q

how to calculate weight?

A

mass (m) x gravitational force per unit mass (g)

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29
Q

if on earth, the gravitational force per unit mass is 10N/kg and an object is 1kg, what is the weight of the object?

A

1 x 10 = 10N

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30
Q

what happens when two or more objects interact?

A

they exert a force on one another, which results in the transfer of energy between the objects

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31
Q

what are examples of transfer of energy between objects causing changes in the state of rest or motion of an object?

A
  • changing the speed of an object
  • moving an stationary object
  • changing the direction of a moving object
  • stopping a moving object
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32
Q

a force applied on an object can cause a ___ which helps us carry out an action with little force

A

turning effect about a fixed point (pivot)

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33
Q

what does “turning effect of a force” mean?

A

when a force is applied on an object off-centre and the object turns about a point called a pivot

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34
Q

how to achieve the greatest turning effect?

A

by applying the force perpendicularly at the furthest distance from the pivot

35
Q

how does forces changes the size and/or shape of an object?

A

the transfer of energy between objects may cause changes in the size and/or shape of an object

36
Q

does the mass of the object change when it changes in shape or size?

A

no

37
Q

what is the definition of pressure?

A

the force exerted per unit area

38
Q

what is pressure determined by?

A

the amount of force acting on the object and the area of contact made on a surface

39
Q

if you were to where heels or sneakers on sand, which type of shoe would exert a greater pressure on the sand? and why?

A

the heel, because the area of contact with the sand is smaller

40
Q

what is the SI unit of pressure?

A

Pascal (Pa) or N/cm^2 and N/m^2

41
Q

how to calculate pressure?

A

pressure = force divided by area

42
Q

is water pressure higher at the top of bottom or a water tank and why?

A

at the bottom because there is more weight exerted there so that makes the water shoot out faster

43
Q

what is atmospheric pressure?

A

pressure exerted by layer of air that surrounds the Earth on us and all objects on earth

44
Q

is there less atmospheric pressure at sea level or at a height above sea level and why?

A

at a height above sea level because the weight of air particles acting on us is less and thus reduces atmospheric pressure exerted

45
Q

what does “work done” mean?

A

when a force applied causes an object to move in the same direction as the force and energy is transferred

46
Q

what is the SI unit for work?

A

Joule (J)

47
Q

what conditions must be satisfied for work to be considered done?

A
  • a force is applied on the object
  • the object moves in the same direction as the force applied on it
48
Q

what is the equation to find work done?

A

Work = F (applied force in newtons) x D (distance moved)

49
Q

when finding work done, the distance should always be measured in?

A

metres

50
Q

when a box is pushed but it remains stationary, is work done?

A

no

51
Q

when a box is carried and a person moves forwards, is work done? why?

A

there is no work done because the box is not moving in the direction of force (upwards)

52
Q

what is the SI unit of energy?

A

Joule (J)

53
Q

what is the law of conservation of energy?

A
  • energy cannot be created or destroyed
  • it can only be converted from one form to another
54
Q

what is kinetic energy (KE)?

A

the energy of an object due to its motion

55
Q

kinetic energy possessed by an object depends on?

A
  • its mass –> the larger its mass, the greater its kinetic energy
  • its speed or velocity –> the faster it moves, the greater its kinetic energy
56
Q

a mass moving with constant speed will have ___ KE

A

constant

57
Q

what is gravitational potential energy (GPE)?

A

the energy stored in an object due to its position in a gravitational field

58
Q

GPE possessed by an object depends on?

A

its weight – the larger its weight, the greater its GPE
its vertical height – the higher it is, the greater its GPE

59
Q

when the carriage is at the top of the roller coaster, it has maximum ___
when the carriage is at the bottom of the roller coaster, it has maximum ___ (so it moves the fastest).

A

GPE ; KE

60
Q

what is the energy conversion from the the top of the roller coaster to the bottom?

A

gravitational potential energy -> kinetic energy

61
Q

when a dancer jumps up into the air (neglecting the effects of air resistance) describe the energy conversion that takes place till the dancer reaches the maximum height

A

chemical potential energy → kinetic energy → gravitational potential energy

62
Q

what are examples of non-renewable energy sources?

A

fossil fuels and nuclear energy

63
Q

what are examples of renewable energy sources?

A

solar energy, biofuels, hydroelectric energy, wind energy and geothermal energy

64
Q

what are fossil fuels?

A

it is formed by the remains of dead plants and animals buried in earth millions of years ago

65
Q

what is the energy conversion of fossil fuels?

A

CPE (fossil fuels) → heat energy → KE (turbine) → electrical energy (generator)

66
Q

what is the impact of fossil fuels on the environment?

A

burning of fossil fuels releases air pollutants and greenhouse gases (which contribute to global warming and increases the rate of climate change) & can cause natural disasters to be more intense

67
Q

what is solar energy and how can we harness it?

A

it’s energy from the sun and we use solar panels made of materials that capture sunlight and convert light energy into electrical energy

68
Q

what is the impact of solar energy on the the environment?

A

solar energy generates electricity without air pollutants or greenhouse gases and has minimal environmental impact, however, reducing toxic waste from solar panel production and disposal is necessary

69
Q

what is the energy conversion of solar energy?

A

light energy (the sun) → electrical energy (solar cell)

70
Q

what is hydroelectric energy?

A

the electrical energy generated by turbines when moving water power thems

71
Q

what is the environmental impact of hydroelectric energy?

A

it produces very little greenhouse gases but the reservoir water floods the area behind a dam which kills plants and forces animals to move to other area

72
Q

what is the energy conversion of hydroelectric energy?

A

gravitational potential energy (water stored behind a dam) → kinetic energy (water) → kinetic energy (turbine) →electrical energy (generator)

73
Q

what is wind energy?

A
  • energy from the wind
  • wind turbines are used to convert the energy from the wind to electrical energy.
74
Q

what is the environmental impact of wind energy?

A
  • large plots of land are cleared to build wind turbines, which destroys the natural habitats of wildlife
  • birds might get killed due to flying into the blades
  • noise pollution from turning blades impacts nearby communities
75
Q

what is the energy conversion of wind energy?

A

kinetic energy (wind) → kinetic energy (wind turbine) → electrical energy (generator)

76
Q

what is geothermal energy?

A

heat stored in the earth that can be harnessed to generate electrical energy

77
Q

what is the environmental impact of geothermal energy?

A
  • its sites require clearing large areas of land which destroys wildlife habitats
  • traces of toxic elements buried underground are also drawn out
78
Q

what is the conversion of geothermal energy?

A

heat energy (Earth’s core) → kinetic energy (steam) → kinetic energy (turbine) → electrical energy (generator)

79
Q

what are biofuels?

A

fuel that is usually made from animal waste or from plant materials that cannot be eaten by humans

80
Q

what is the environmental impact of biofuels?

A
  • burning of biofuels releases air pollutants such as carbon dioxide into the environment
  • plants grown for making biofuels carry out photosynthesis so the amt of CO2 taken in helps balance the amt of CO2 released when the biofuel are burnt
81
Q

what is the energy conversion of biofuels?

A

chemical potential energy (biofuel) → heat energy (when burned) → kinetic energy (vehicle)

82
Q

what is nuclear energy?

A

energy harnessed from the nucleus of an atom (this energy can be obtained through nuclear reactions and then converted to electrical energy)

83
Q

what is the environmental impact of nuclear energy?

A
  • it’s a clean energy source and requires less land space to generate the same amount of energy compared to other sources of energy
  • research is ongoing to develop newer & safer ways to generate energy from nuclear reactions
84
Q

what is the energy conversion of nuclear energy?

A

nuclear energy (atoms) → heat energy → kinetic energy (turbine) → electrical energy (generator)

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