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Common q Flashcards

pair with defintions and chapters + ultrasound + electromagnetic forces + electromagnetic induction

1
Q

As the trolley moves across the rough surface, it slows down and stops.
Explain, in terms of the work done, the energy change that takes place as the trolley slows down.

A

work done against friction

kinetic energy transfers to thermal energy, so thermal energy is produced

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2
Q

Why a bus begins to topple?

A

The centre of mass would be to the right of the ‘pivot’ (the right-hand wheel) which would exert a
clockwise moment.

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3
Q

State the principle of the conservation of momentum.

A

the total momentum is constant and does not change because of an interaction between bodies such as collisions

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4
Q

State the principle of conservation of energy.

A

energy cannot be created or destroyed; it can only be stored or transferred

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5
Q

State two properties of an object that may be changed by the action of forces.

A

size, shape (direction of motion, velocity)

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6
Q

State the two conditions which must be true for an object to be in equilibrium.

A

no resultant force, no resultant moment

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7
Q

Hooke’s law

A

the extension of an object is proportional to the load producing it

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8
Q

Explain what is meant by the term limit of proportionality of the spring.

A

up to this limit, Hooke’s law s obeyed (so extension is proportional to load)

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9
Q

What type of energy is stored in springs?

A

elastic energy.

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10
Q

Describe and explain the motion of an object released from top of an fluid, from when it is released until it reaches terminal velocity.

A

Initial acceleration caused by weight.
Air resistance increases with speed of motion.
Acceleration decreases as air resistance increase.
When weight= air resistance there is no resultant force. He falls at terminal velocity when resultant force is 0.

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11
Q

Explain why opening the parachute cannot reduce the speed of the skydiver to zero.

A
  1. Open parachute causes air resistance. At zero speed, there is no air resistance.
  2. Weight is acting downwards.
  3. Forces can only balance at a speed greater than zero, so no decrease in speed.
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12
Q

Why not 100% of GPE is converted to KE when an object falls?

A

work done against friction and thermal energy generated

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13
Q

Describe the arrangement, separation and motion of particles in a gas.

A

Random arrangement. Widely spaced. Move randomly and freely (colliding with each other and walls) at high speeds.

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14
Q

Describe the arrangement, separation and motion of particles in a solid.

A

Regular arrangement. Tightly packed. So cannot move around (vibrate in fixed positions, the hotter= more)

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15
Q

State two ways in which a liquid is different from a solid.

A

Arranged randomly. Less tightly packed close together. (not in a fixed position), moves around and vibrates

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16
Q

Describe, in terms of molecules and their motion, how a liquid differs from a gas.

A

molecules closer
molecules do not move freely
molecules vibrate and move

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17
Q

Why solids have fixed shapes? Explain in terms of forces between molecules and arrangement of molecules.

A

regular lattice arrangement, particles are packed tightly together, strong forces between molecules

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18
Q

Why liquids adapt to the shape of their container? Explain in terms of forces
between molecules and arrangement of molecules.

A

particles are free to move within liquid, no fixed shape, irregular lattice arrangement, forces weak

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19
Q

Why gas fills their container? Explain in terms of forces between molecules and
arrangement of molecules.

A

weak forces, far apart and move freely as well as randomly

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20
Q

Explain the melting of a solid in terms of molecules and energy.

A

Temperature stays the same while melting. Energy is required to break bonds which is provided by heating.

Molecules gain energy and move faster. Molecules are now slightly further apart. The solid expands as it melts.

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21
Q

The gas bubble rises to the surface. The volume of the gas bubble increases as it rises higher in the water. Explain why the volume of the bubble increases.

A

pressure decreases with depth, pressure is inversely proportional to volume

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22
Q

Explain, in terms of particles, why it is difficult to compress liquids.

A

particles are close together, forces between particles are large

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23
Q

Sound waves are diffracted through doorways. Light waves from a television are not diffracted through doorways. Suggest why light waves and sound waves behave differently in this situation.

A

Wavelength of light is smaller than wavelength of sound.

The greater the wavelength of waves the greater the angle they are diffracted. = Small gaps are needed to see light being diffracted.

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24
Q

Longitudinal Vs Transverse

A

longitudinal: rarefactions and compressions
transverse: crests and troughs

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25
Q

Define compression and rarefaction.

A

region of sound wave where particles are pushed together/further apart, so the region is (less) dense

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26
Q

What are:
seismic waves
P-waves
S-waves

A

seismic: waves caused by earthquakes
P-waves: fast-moving, longitudinal seismic waves
S-waves: slow-moving, transverse seismic wave-

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27
Q

Frequencies that humans can hear?

A

20-20000Hz

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28
Q

Sounds are caused by..

A

vibrating sources

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29
Q

The sound wave passes from the sea-water into the air. What happens to the frequency, wavelength and speed?

A

speed decreases, frequency remains the same, wavelength decreases

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30
Q

Loudness is increased, what happens to the amplitude and wavelength?

A

Wavelength stays the same, amplitude increases.

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31
Q

Pitch is increased, what happens to the amplitude and wavelength?

A

Amplitude stays the same, wavelength decreases.

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32
Q

High frequency means..
High amplitude means..

A

high pitch
loud sound

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33
Q

Define wavelength.

A

the distance between two adjacent crests (or troughs)

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34
Q

Define frequency.

A

the number of complete vibrations or waves per unit time

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35
Q

How does a wavelength look?

A

Two big loops, 4 halves

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36
Q

Where are the crest and trough located?

A

Crest is top point, trough is bottom point

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37
Q

Reflection definition

A

the change in the direction of a ray -> when it strikes a surface without passing through it (can also occur in waves)

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38
Q

Define refraction

A

the bending of light when it passes from one medium to another (can also occur in waves)

{rays are closer to the normal, slow at the shallow, ‘light rays’ at right angles to ripples, submerged glass plate for depth}

39
Q

Define diffraction

A

when a wave spreads out as it travels through a gap or past the edge of an object

40
Q

Refractive index formulas

A

n=sini/sinr
n=1/sinc
n=speed of light in air/speed of light in oil

41
Q

What are the uses of radio waves?

A

broadcast radio and television signals, radio astronomy, radio frequency identification (RFID), Bluetooth, wifi

42
Q

What are the uses of microwaves?

A

microwave ovens, satellite television broadcasting, transmit mobile phone signals

43
Q

What are the uses of infrared radiation?

A

remote controls in devices such as televisions, grills and toasters, security alarms, optical fibres, medicine: detect heat which may indicate infection or to speed up healing and reduce pain

44
Q

What are the uses of visible light?

A

to see, optical instruments such as cameras, telescopes and microscopes, photosynthesis

45
Q

What are the uses of ultraviolet light?

A

forensic scientists find evidence at crime scenes not visible to the eye, security marking of valuable equipment and banknotes, sterilise water

46
Q

What are the uses of x-rays?

A

security scanners at airports, see inside patients without surgery (bones absorb x-rays so it will appear as a shadow on the shadowgraph)

47
Q

What are the uses of gamma rays?

A

damage or kill living cells (such as cancerous cells), sterilise surgical instruments, detection of cancer

48
Q

Describe the advantages of using ultrasound waves instead of x-rays.

A

not dangerous= cannot harm the tissues, DNA damaged= genes may be passed on and mutation can occur in the offspring which is often harmful

49
Q

Explain, in terms of wave theory, what occurs as the wavefront strikes the boundary.

A

i=r, moves at same speed

50
Q

To calculate how many kilometres away is a storm,

A

measure the time between, and divide by 3

51
Q

Describe how the movement of the loudspeaker cone produces these regions of different
pressure.

A

Cone moves forward and pushes air particles together. Cone moves backwards which allows for more space between air particles.

52
Q

The man with his ear to the railway line actually hears two sounds from the hammer,
separated by a short interval.
Explain why he hears two sounds.

A

sound through air and sound through steel

speeds in air and steel are different

53
Q

Define electromagnet.

A

a coil of wire that acts as a magnet when an electric current passes through it

54
Q

Define solenoid

A

an electromagnet made,
by passing a current,
through a coil of wire

55
Q

How can you increase the strength of an electromagnet? How can the field be reversed?

A

greater current, number of turns, add soft iron core (ctc)

reversing the direction of the current

56
Q

Magnetism rules

A

Magnetic materials can be magnetised. Becomes a magnet when magnetised. Non-magnetic materials cannot be magnetised

57
Q

The north pole is brought close to the pin, what pole is induced?

A

south, so they attract

pin will return to unmagnetised state or may retain a small amount of magnetism

58
Q

draw an eye suitably placed to view the image I.

A

wide part of defined light rays, to the right of lens

59
Q

Describe one example of how optical fibres are used in medicine.

A

Light travels down in the optical fibres and back upwards in an endoscopy, which allows the doctor to see so they can examine or do surgery on an organ.

60
Q

A wave enters glass, what happens to its speed, frequency and wavelength?

A

speed decreases, frequency unchanged, wavelength decreases

(light and waves work the same)

61
Q

As light enters glass, what happens to its speed, frequency and wavelength?

A

speed decreases, frequency unchanged, wavelength decreases

(light and waves work the same)

62
Q

State an application in which a convex lens is used in this way. Image is magnified.

A

magnifying glass

63
Q

State the term which describes the separation of red and violet refracted rays in glass.

A

dispersion of light

64
Q

Explain, in terms of molecules, why a liquid expands when heated.

A

molecules gain kinetic energy and move faster
molecules push others away and move further apart

65
Q

Why does thermal expansion happen?

A

Particles gain energy and move faster, pushing each other further apart.

66
Q

Explain, in terms of forces between molecules, why gases expand more than liquids when they have the same rise in temperature. Assume that the pressure remains constant.

A

Forces weaker. Particles are close together and free to move. Easy to push neighbours aside.

67
Q

Expansion of a gas.

A

Particles gain energy, move faster and push with greater force. Particles are further apart.

68
Q

What are rivets used for?

A

Used in shipbuilding and other industries.

69
Q

Explain the joining of two metal plates using a rivet?

A

A red-hot rivet is passed through holes in the two metal plates and then hammered until the ends are rounded.

As the rivet cools, it contracts and pulls the two plates together tightly.

70
Q

A metal lid or cap may stick on a glass jar or bottle and be hard to unscrew.

A

Heating the lid (eg: under running hot water) causes it to expand. The glass expands less than the metal lid, so the lid loosens and can be removed.

71
Q

Explain how a steel ‘tyre; can be fitted on the wheel of a train.

A

Fitted while it is very hot. Cools and contracts so that it fits tightly on the wheel.

72
Q

A bimetallic strip is designed to bend as it gets hot.

A

The strip is made of two metals joined firmly together. One metal expands much more than the other.

As the strip is heated, this metal expands, causing the strip to bend. The metal that expands more is on the outside of the curve, because the outer curve is longer.

73
Q

What are bimetallic strips used in?

A

Devices such as fire alarms and thermostats. Thermostats are used to control the temperature of devices such as ovens and irons.

74
Q

Consequence of expansion for railway lines plus a solution.

A

Railway lines expand on hot days and there is danger that they might bend.

Railway line are made of a metal alloy that expands very little.

75
Q

Explain the consequences of expansion for bridges and suggest a solution.

A

Metal bridges expand on hot days and there is danger that they might bend.

Bridges are made in sections with expansion joints between the sections. On a hot day, the bridge expands and the gap between sections decrease. Interlocking teeth of expansion joint move closer together.

76
Q

Describe the consequences of expansion for road surfaces.

A

Road surface of concrete roadway is in short sections. Gaps between are filled with soft tar, which becomes squashed as the road expands.

77
Q

State economic and environmental consequences of producing nuclear waste.

A

stored with shielding, stored securly, transported with shielding

78
Q

Name the energy store in the battery

A

chemical energy store

79
Q

State one advantage of a parallel connection in a lighting circuit.

A

if one lamp breaks, the other one will remain lit

80
Q

Suggest two advantages of using a solar cell to power the traffic warning lights
compared to using mains electricity

A

no need for cables
less power loss
not affected by mains power cuts

81
Q

Explain why the seesaw rotates clockwise.

A

clockwise moment has increased

82
Q

Explain how the rubber floor reduces injury to the child.
Use ideas about impulse, force, momentum and time in your answer.

A

Impulse is the same for both floors
Impulse acts over a longer time
Less force on child

83
Q

State what happens to the water particles as the water temperature increases.

A

ke of particles increase, so move faster

84
Q

Suggest why the actual time taken to heat the water is longer. Assume that the student takes accurate measurements

A

thermal energy is transferred to the environment

85
Q

The specific heat capacity of stainless steel is 500J/(kg°C).
The specific heat capacity of aluminium is 890J/(kg°C).
Explain how using an aluminium saucepan will affect the time taken to heat the water

A

Takes longer. More energy needed for same temp increase. Higher c.

86
Q

Describe three similarities between the use of ultrasound and X-rays in medical scanning procedures.

A
  • show internal body parts without need to cut
  • travel through the body
87
Q

Describe three differences between the use of ultrasound and X-rays in medical
scanning procedures.

A
  • x-ray exposes you to radiation
  • ultrasound detector forms an image from reflected sound waves
  • x-ray shows bones, ultrasound shows soft tissue
88
Q

Convert kWh to J.

A

1 kW h = 1000 x 60 x 60 J

AND value x answer

89
Q

The charging plate has a useful output power of 15 W.
The manufacturer claims that the battery can be charged to 50% in less than 30 min.

A

50% of energy is..

P=W/T

P=W/T with the half being the work

24 min is less than 30 min

90
Q

The train uses electric motors.
Explain why the force on the train due to the motors is greater than the value calculated
in (ii).

A

Additional force needed to overcome friction

91
Q

State two ways that evaporation differs from boiling

A
  • happens only at the surface
  • takes place at any temperature
92
Q

Internet data can be transferred using infrared waves in optical fibres.
State two advantages of using optical fibres to transmit data.

A

high rate of data transmission
carry large amounts of data

93
Q

Explain why this graph cannot be used to find the wavelength of the sound wave.

A

graph does not show variation with displacement

94
Q

A student is given the three pieces of steel. Two of the pieces are magnetised and one piece
is unmagnetised.
Describe and explain how the student determines which piece is unmagnetised using only
the three pieces of steel.

A

One end close to other. See if there is attraction/repulsion.

Attraction at both ends mean one of them is unmagnetised. Only magnets repel each other.

PT (15 decks)

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