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Physics > EOY > Flashcards

EOY Flashcards

1
Q

Elastic deformation

A

When an object returns to its original shape when the stretching force is removed

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2
Q

equation with force, spring constant and extension

A

f = ke

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3
Q

equation for elastic potential energy

A

EPE = 1/2ke^2

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4
Q

Inelastic deformation

A

when an object does not return to its original shape when the stretching force is removed. Therefore, it is left permanently stretched

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5
Q

What is Hooke’s Law?

A

The extension of a spring is directly proportional to the force applied to it, as long as its limit of proportionality is not exceeded.

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6
Q

Limit of proportionality

A

The limit of proportionality is where if more force is added, the object will not return to its original shape when the force is removed

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7
Q

How to tell if object contains elastic potential energy?

A

it will return to its original shape

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8
Q

Explain why adjusting the ruler was important

A

to reduce error in measuring the extension of the spring

the ruler at an angle will make the measurements shorter

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9
Q

how to know if something is directly proportional

A

straight line

that passes through the origin

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10
Q

Technique to improve measuring extension

A

attach a pointer to the bottom of the spring

so it goes across the ruler scale

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11
Q

The stiffer the spring

A

the greater the spring constant, therefore more force is required per metre of extension

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12
Q

spring constant on a force-extension graph

A

is the gradient

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13
Q

steep straight line on force-extension graph =

A

small spring constant

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14
Q

work done is

A

the transfer of energy

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15
Q

Elastic potential energy

A

The energy stored in an elastic object when work is done on the object

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16
Q

types of errors

A 
systematic error (zero error)
random error
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17
Q

Newton’s Second Law of Motion?

A

When a resultant force acts on an object, it produces an acceleration (or deceleration)

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18
Q

What is Newton’s First Law of Motion?

A

If no resultant force acts, an object will remain stationary or move at a constant speed in the same direction

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19
Q

What is Newton’s Third Law of Motion?

A

When two objects interact with each other, they exert equal and opposite forces on each other

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20
Q

effects on stretched coil

A

the length of the coil has increased
length of the loops has stretched
spring has stretched

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21
Q

why are mean values given to 2 dp if results are 3 dp?

A

stopwatch reacts to 0.01 s

reaction time is less precise than a stopwatch

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22
Q

acceleration

A

the rate of change of velocity

change in velocity / time taken

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23
Q

velocity

A

the rate of change of displacement

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24
Q

accelerate

A

changed velocity

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25
Q

speed of sound

A

330 m/s

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26
Q

human walking speed

A

1.5 m/s

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27
Q

human running speed

A

3 m/s

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28
Q

human cycling speed

A

6 m/s

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29
Q

distance in a velocity-time graph

A

area under the graph

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30
Q

How to calculate reaction time

A

measure the distance the ruler falls before being stopped - the greater this distance the greater the reaction time
repeat measurements and calculate mean

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31
Q

why were anomalous result during reaction time

A

the student was distracted

stopwatch started before the computer test was started

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32
Q

How would you increase speed of a car

A

make it more streamlined
reduce the weight
increase power of engine

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33
Q

contact forces

A 
forces that act between objects that are physically touching
e.g.
tension
friction
air resistance 
reaction force
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34
Q

resultant force

A

a single force that has the same effect as all the forces combined operating on an object

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35
Q

why does acceleration decrease even though the force remains constant

A

as speed increases air resistance increases

reduces the resultant force

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36
Q

why might an object continue at the move at a constant speed in the same direction

A

the resultant force is equal to 0

so the object will move at the same speed in the same direction

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37
Q

if an object is more streamlined

A

the air resistance is smaller

so the object can reach a higher speed

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38
Q

distance in a velocity-time graph

A

1/2 x base x height

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39
Q

Explain how the wheel can move at a steady speed and the capsules accelerate at the same time.

A

acceleration occurs when the direction of each capsule changes
acceleration is the rate of change of velocity

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40
Q

scalar quantities

A 
have size (magnitude) but no specific direction
e.g. speed, direction, mass, temperature & time
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41
Q

vector quantities

A

have both magnitude and direction

e.g. force, acceleration, displacement, velocity & weight

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42
Q

What are waves

A

are repeated vibrations that transfer energy from one place to another

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43
Q

What is the time period (waves)

A

time it takes for one complete oscillation

44
Q

wave speed equation

A

wave speed (m/s) = frequency (Hz) x wave length (m)

45
Q

Transverse waves

A

the oscillations are perpendicular to the direction of energy transfer
e.g. electromagnetic, ripples on the surface of water, vibrations in guitar strings and seismic S waves

46
Q

Longitudinal waves

A

the oscillations are parallel to the direction of energy transfer
e.g. sound, seismic P waves

47
Q

Non contact forces

A

don’t require the objects to be touching
e.g. gravitational, electrostatic and magnetic
get weaker the further the object is from the force

48
Q

Ray diagrams (reflections)

A

angle of incidence = angle of reflection
normal is perpendicular to the surface of the material
point of incidence is where incoming ray touches the boundary

49
Q

Specular reflection

A

mirrors are perfectly smooth - so boundary is flat
all the normals point towards the same direction
gives a clear image

50
Q

diffuse/scattered reflection

A

when boundary is bumpy (e.g. paper)
normals are in different directions
you can’t see yourself

51
Q

frequency of a wave

A

always stays the same - only the wavelength changes

52
Q

when can waves change direction

A

when they change speed, moving from one medium to another

different mediums have different densities

53
Q

if waves enter or leave the medium at right angles to the surface

A

they do not change direction (along the normal)

54
Q

the higher the density of the material

A

the slower the wave will travel

55
Q

Describe the movement of a wave refracted in glass

A

the wave hits the boundary at an angle
if it passes into a more dense medium (ie glass) then the ray will slow down and bend towards the normal
when it passes out into a less dense medium (ie air)
then the ray will speed up and bend away from the normal

56
Q

wavefront

A

is an imaginary line that connects all the same points in a set of waves
they make it easier to visualise lots of waves moving together

57
Q

Movement of wave fronts from air into glass

A

as the wavefronts move into the glass, they slow down
this causes the wavefronts to get closer together
which causes the wavelength to get smaller
this causes the wave to bend towards the normal
when waves speed up they bend away from the normal

58
Q

compressions

A

regions where the vibrating particles are closest together

59
Q

rarefractions

A

regions where the vibrating particles are further apart

60
Q

The more densely packed the particles are

A

the faster the sound travels

sound waves need particles to be transmitted

61
Q

when sound travels through a solid

A

they cause particles in the solid to vibrate
the vibrating particles will collide with their neighbours
which pass on the vibration
eventually the sound wave is transmitted through the material

62
Q

sound waves are transmitted faster

A

through solid

slower through gases

63
Q

Why can’t sound travel through a vacuum

A

there are no particles for the sound to be transmitted

64
Q

wavelengths get longer as sound

A

speeds up

shorter as sound slows down

65
Q

sound can be

A

reflected, absorbed and refracted

66
Q

How do sound waves travel through an ear

A

sound waves travel along the ear canal and hit our eardrums
this causes the eardrums to vibrate
the vibrations are transmitted along the ossicles, through the semicircular canals and into the cochlea
the cochlea converts the vibrations into electrical signals, which are then sent along the auditory nerve to the brain and converted into sounds

67
Q

higher frequency sounds

A

higher pitch sounds

68
Q

lower frequency sounds

A

lower pitch sounds

69
Q

Human hearing range

A

20Hz - 20,000Hz

70
Q

why does human hearing range decrease

A

due to age

from the wear and tear of the cochlea and auditory nerve

71
Q

ultrasounds

A

sounds that vibrate at frequencies above 20,000Hz

72
Q

why do animals produce ultrasound

A

for communication

for echo location

73
Q

why are ultrasounds partially reflected

A

some of the waves are reflected when they hit a boundary

whereas some are transmitted through (where they are refracted)

74
Q

Uses of ultrasound

A 
identify the boundaries within an object - which helps determine its internal structure
check the quality of products in industry - if there is a crack, waves will be reflected back
echo sounding (sonar) - when boats or submarines fire ultrasounds at the seafloor to find out how far away it is
75
Q

P-waves (seismic)

A

longitudinal
travel through liquids and solids
faster than s-waves

76
Q

S-waves (seismic)

A

transverse
travel through solids
slower than P-waves

77
Q

P-waves through the earth

A

as p-waves are transmitted through the earth, they are refracted
the p-waves are constantly refracted throughout each layer (mantle, liquid outer core) as the density isn’t the same throughout a layer

78
Q

battery

A

2 or more cells

79
Q

potential difference

A

V = IR

80
Q

current flows

A

from positive to negative (conventional current)

81
Q

diodes

A

only allow current to flow in one direction
have a really high resistance in the reverse direction
only show when PD is positive

82
Q

As potential difference increases

A

current also increases proportionally
assuming resistance is constant
assuming temperature is constant

83
Q

if temperature increases

A

resistance increases

84
Q

filament

A 
as the current flows through the filament
wire heats up
eventually displays light
however, this increases resistance
so curve becomes less steap
85
Q

series circuit

A

potential difference of the battery is shared across all components
current is the same
total resistance = sum of the individual resistance of all the components
greater the resistance the higher the voltage the component shares

86
Q

parallel circuits

A

more components in parallel = lower total resistance
p.d. of components = p.d. of battery
current = sum of individual components
higher the resistance = lower share of the current

87
Q

fuses break if

A

too much current

88
Q

Ammeter

A

measure current

connected in series

89
Q

Voltmeter

A

measure p.d.

connected in parallel

90
Q

LDR

A

resistor dependent on the intensity of light
dark = high resistance
light = low resistance

91
Q

uses of LDR

A

automatic night lights

burglar alarms

92
Q

thermistor

A

resistance is dependent on temperature
hot = low resistance
cold = high resistance

93
Q

uses of thermistor

A

car engines

electronic thermostats

94
Q

Charge

A

measure of the total current that has flowed within a period of time

95
Q

Charge equation

A

Q (coulombs) = I x t

96
Q

why cant you increase current to increase power

A

high current = lots of heat (because of the resistance)

so lots of energy would be lost

97
Q

Power equation

A

P = VI

98
Q

Journey of national grid

A

power stations –> step up transformers
(increase the p.d. to 400,000 V)
—> pylons transmit the electricity —> step down transformers
(decrease p.d. to 230V)

99
Q

national grid

A

It consists of a system of cables and transformers linking power stations to consumers (houses, factories and buildings).

100
Q

why do step-up transformers increase voltage

A

to minimise energy loss during transmission

101
Q

why do step-down transformers reduce voltage

A

to make it safe to use

102
Q

alternating current

A

constantly changes direction
has 2 identical terminals
occurs when we use alternating p.d.
e.g. mains supply

103
Q

direct current

A

constantly flows in the same direction
either positive or negative
has fixed positive and negative terminals
e.g. batteries and cells

104
Q

oscilloscopes

A

display a.c and d.c current

105
Q

electromagnetic waves travel at

A

3 x 10^-8 m/s in a vacuum

Physics (9 decks)

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