Prac Task Yr 11 Module 3

Question 1

Define validity

Answer 1

Validity refers to whether all the variables within an experiment, apart from the independent and dependent, were controlled.

Question 2

Define accuracy

Answer 2

The accuracy is how close the final result is to the accepted or correct value

Question 3

Define reliability

Answer 3

Reliability is how close repeated measurements are to each other.

Question 4

Types of metric prefixes

Answer 4

Thieves Graded Minesweepers Kindly However DAshing Dilbert Captured Musty Mickey Nelly Poignantly

Question 5

Formula for wave number

Answer 5

The number of waves per unit distance
𝑘=2𝜋/𝜆
waves per metre (m-1)

Question 5

Define wave

Answer 5

Waves: disturbance that travels through medium from the source to the detector without any movement of matter.
Transfer energy without movement of particles

Question 6

Define periodic waves

Answer 6

Periodic waves: disturbances that repeat at regular intervals. Propagate by disturbance in part of a medium passing on to its neighbours. This causes disturbance to travel but medium to become stationary. Ripples in pond

Question 7

Transfer of energy in transverse or longitudinal waves

Answer 7

A transverse wave is one in which the disturbance caused by the transfer of energy acts perpendicularly to the direction of the wave itself.

Longitudinal (compression): disturbance moves parallel to wave direction. As disturbance moves through particles, it alternately pushes them closer together and then far apart

Question 8

Define amplitude

Answer 8

Transverse waves: The amplitude is the maximum displacement, that is the height of each crest above, or depth of each trough, the mean position of the medium. Amplitude has units of metres.
Longitudinal waves: The amplitude is the maximum displacement of the particle from its equilibrium position as shown below.

Question 9

Define wavelength

Answer 9

Transverse wave: The wavelength is the distance between successive crests, or successive troughs.
Longitudinal wave: The wavelength is the distance between successive compressions, or successive rarefactions.

Question 10

Define frequency

Answer 10

Transverse wave: The frequency, f, is the number of crests, or troughs, going past a fixed point in the medium in one second.
Longitudinal wave: The frequency is the number of compressions, or rarefactions, going past a fixed point in the medium in one second.

Question 11

Define period

Answer 11

Transverse wave: The period is the time between successive crests, or troughs, to go past a fixed point in the medium.
Longitudinal wave: The period is the time for successive compressions, or successive rarefactions, to go past a fixed point in the medium.

Question 12

Difference between mechanical and em waves

Answer 12

Mechanical waves involve the transfer of energy through a medium by the motion of the particles of the medium itself.
Electromagnetics waves are transverse waves that consist of alternating electric and magnetic force fields positioned perpendicular to each other and to the direction of energy propagation. Electromagnetic waves do not need a medium to travel in.
Decelerate when in physical mediums apart from a vacuum.

Question 13

Do waves lose energy

Answer 13

As electromagnetic waves do not need the movement of any particles to propagate (as mechanical waves do), they do not lose energy due to friction between particles.

However, because mechanical waves transfer energy by means of particle vibration, energy is lost, due to friction, over the course of the wave transmission through the medium.

Question 14

Define wave interference

Answer 14

Phenomenon that occurs when two waves meet whilst travelling along the same medium. Interference causes the medium to take on a shape resulting from the net effect of two individual waves upon particles of the medium.

Question 15

Define superposition

Answer 15

Superposition: when waves in a medium interfere with each other, amplitude of the individual wave pulses add together to give amplitude of total disturbance of medium

Question 16

Position of Antinode vs node

Answer 16

2 nodes in first harmonic and 1 antinode
Antinode between nodes

Question 17

Define natural vibration

Answer 17

Natural vibration: rate at which object oscillates at the same rate regardless of how hard it is hit, due to vibrational rate being determined by metal it is made from, its length and spacing of its prongs.

Question 18

When does forced vibration occur

Answer 18

Occurs when an object is compelled to vibrate by placing it in contact with another vibrating object. Is necessary for sound amplification.
Frequency of forced vibration is referred to as driving frequency.

Question 19

When does resonance occur

Answer 19

Occurs when object is exposed to driving frequency equal to object’s natural frequency. Has the effect of increasing the amplitude of object’s vibration due to constructive interference.

Question 20

How is sound produced

Answer 20

Sound is produced by varying air pressures that produce a vibration effect in air particles resulting in zones of high air pressure (compression) and zones of low pressure (rarefaction)

Question 21

Factors which influence sound

Answer 21

Pitch: the rate at which vibrations are produced. The higher the frequency, the higher the pitch

Loudness: dependent on strength or amplitude of vibrations producing the sound

Question 22

Describe sound wave

Answer 22

Sound is a longitudinal wave. It travels through a medium. It pushes the particles of substances which push into other particles adjacent to it and then return to their original position. This movement continues until it reaches the ear.

Question 23

Describe sound intensity
To find I equation

Answer 23

Intensity of sound wave is a measure of the amount of energy able to transfer to a square metre of surface in a 1 second interval.
I=P/A
I=P/4πr²
measured in W m^-2

Question 24

Describe acoustic power

Answer 24

Acoustic power of source: The amount of sound energy produced by a source every second.
Measured in joules
P=E/t
unit of power is Js–1
Referred as a watt (W).
Inverse square law
𝐼∝ 1/𝑟^2

Question 25

Formula for sound intensities

Answer 25

When comparing the sound intensities at two distances r1 and r2 from a source, it should be remembered that the power of the source is a constant. This relationship then gives the following useful formula:
𝐼_2/𝐼_1 =(𝑟_1^2)/(𝑟_2^2 )
I1r1^2=I2r2^2

Question 26

When are beat frequencies created

Answer 26

Beat can be created when two waves with the same amplitude with slightly different frequencies are superimposed (two transverse waves come together, and their frequencies cancel) to produce pulses or beats.
=difference in frequencies
=|𝑓1−𝑓2 |

Question 27

Define doppler effect

Answer 27

The apparent change in frequency of a wave caused by relative motion between the source of the waves and the observer.
f’=f (vwave + vobserver)/(vwave-vsource)
f’: apparent or observed frequency
f: original frequency
vwave: speed of waves in the medium
Vobserver: speed of observer relative to the medium
Vsource: speed of source relative to the medium
NOTE: If the sound source is coming towards the observer, then 𝒗_𝒔𝒐𝒖𝒓𝒄𝒆 will be positive.
If the sound source has passed the observer, then 𝒗_𝒔𝒐𝒖𝒓𝒄𝒆 is a negative value.

Question 28

Define standing wave

Answer 28

Two waves with the same amplitude, wavelength and frequency travelling in opposite directions will interfere and produce a combined wave.
Frequencies that produce standing waves are called resonant frequencies.

Question 29

Difference between constructive and destructive interference

Answer 29

Constructive interference: Two waves overlap in such a way that they combine to create a larger wave
Occurs at antinodes
Destructive interference: Two waves overlap in such a way that they cancel each other out
Occurs at nodes

Question 30

Formulas for strings with fixed ends

Answer 30

λ=2l/n
First harmonic (fundamental frequency)
f=v/λ=v/2l
Second harmonic:
f=v/λ=v/l
Third harmonic:
f=v/λ=3v/2l
Fourth harmonic:
f=v/λ=2v/l
f=nv/2l

Question 31

Formulas for strings with one fixed and open end

Answer 31

λ=4l/n
f=nv/4l
Only odd-numbered harmonics are possible as they can only satisfy the conditions of having a node at the fixed and antinode at the open end.

Question 32

Formulas for pipes with open ends

Answer 32

f=nv/2l
λ=2l/n

Question 33

Define diffraction

Answer 33

Diffraction: A wave remains in the same medium but bends around an obstacle or passes through an aperture

Question 34

Define medium

Answer 34

Medium: Matter that waves travel through

Question 35

Define progressive wave (travelling wave)

Answer 35

A wave which travels continuously in a medium in the same direction without a change in its amplitude

Question 36

Define propogation

Answer 36

Propagation: Process by which a wave transmits through a medium

Question 37

Define oscillation

Answer 37

Oscillation refers to the repeated back and forth movement of something between two positions or states. An oscillation can be a periodic motion that repeats itself in a regular cycle.

Question 38

Define refraction

Answer 38

Refraction: Change in direction and wavelength when a wave moves from one medium to another
When waves slow down they bend ‘towards the normal’.
When waves speed up they bend ‘away from the normal’.

Question 39

Refractive Index formula

Answer 39

n𝑥=c/v𝑥
n𝑥: refractive index of medium 𝑥 (no units)
c: speed of light in vacuum
v𝑥: speed of light in medium
n1v1=n2v2
n1: refractive index of first material
n2: refractive index of second material
v1: speed of light in first material
v2: speed of light in second material

Question 40

Snell’s law

Answer 40

𝑛_1 sin⁡𝑖=𝑛_2 sin⁡𝑟
OR
𝑛_1/𝑛_2 =sin⁡ 𝜃2/sin⁡𝜃1
n1: refractive medium of incident medium
n2: refractive medium of refracting medium
i: angle of incidence (𝜃1)
r: angle of refraction (𝜃2)

Question 41

Define dispersion

Answer 41

Dispersion is defined as the spreading of white light into its full spectrum of wavelengths.
When we view all of the colours of visible light mixed together, our eyes and brain interpret the result as ‘white light’.
Can see different colours because waves of different wavelengths are slowed down or speed up by different amounts as they travel into a medium.

Question 42

Define critical angle

Answer 42

Total internal reflection only occurs when the wave goes from slower to faster (ie, it speeds up).
The critical angle (θc) is the incident angle that causes an angle of refraction of 90° (ie, the refracted ray travels along the edge of the boundary).

Question 43

Critical angle formula

Answer 43

Critical angle can be calculated using:
sin⁡𝑖𝑐 =1/𝑛𝑥

𝑖𝑐= 𝑐𝑟𝑖𝑡𝑖𝑐𝑎𝑙 𝑎𝑛𝑔𝑙𝑒
𝑛𝑥=refractive 𝑖𝑛𝑑𝑒𝑥 𝑜𝑓 𝑚𝑒𝑑𝑖𝑢𝑚

Question 44

Why can humans see

Answer 44

We can see objects because light bounces off them and hits our eyes.
Light travels in straight lines
With a plane mirror, the light has left an object, reflected from the mirror, and hit our eyes.

Question 45

Define centre of curvature, optical centre and radius of curvature

Answer 45

The centre of curvature (C) is the geometric centre of the sphere of which the curved mirror is a section.
The optical centre (O) is the centre of the curved mirror’s face.
The radius of curvature (R) is the radius of this sphere; this will be the distance between the centre of curvature and the geometric centre of the mirror.

Question 46

Define principal focus, principle axis and focal length

Answer 46

The principal focus (F) is the point at which the reflected rays converge when the incident rays are parallel to the principal axis (concave mirror) or the point from which diverging reflected rays appear to originate (convex mirror).
The principal axis is the line upon which the centre of curvature, the principal focus and the optical centre lie.
The focal length (f) is the distance between the principal focus and the optical centre. For a spherical mirror, the focal length is half the radius of curvature.

Question 47

Difference between convex and concave

Answer 47

A concave mirror is a spherical mirror with an inwardly curved reflection surface, whereas a convex mirror is a spherical mirror with an outwardly bulged reflecting surface.

Question 48

Define temperature

Answer 48

A measurement of the average kinetic energy (movement) of the particles.

Question 49

Define heat

Answer 49

is the transfer of thermal energy from a hotter body to a colder one.

Question 50

What happens when a solid substance is heated in terms of particles?

Answer 50

When a solid substance is heated, the particles within the substance gain either:
kinetic energy (move faster), or
potential energy (move away from their equilibrium positions).

Question 51

When is thermal equilibrium achieved?

Answer 51

When touching objects within a system reach the same temperature

Question 52

What is the Zeroth law of thermodynamics

Answer 52

If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.

Question 53

What is the first law of thermodynamics?

Answer 53

First law of thermodynamics – Energy can neither be created nor destroyed. It can only change forms. In any process, the total energy of the universe remains the same. For a thermodynamic cycle the net heat supplied to the system equals the net work done by the system.
Change in internal energy of air=Heat energy applied to air - work done by air
ΔU=Q - W

Question 54

Define specific heat capacity

Answer 54

the amount of energy required to increase the temperature of 1 kg of the substance by 1°C (or K).

Question 55

Example of specific heat capacity

Answer 55

It takes more energy to increase the temperature of water by 1°C than any other common substance. Water also needs to lose more energy to decrease in temperature. In simple terms, this means that water maintains its temperature well, cooling down and heating up more slowly than other materials.

Question 56

Why do specific heat capacities differ

Answer 56

the different contributions to the internal energy by the forms of energy other than translational kinetic energy, and
the varying mass of individual atoms and molecules.

Question 57

Specific heat capacity formula

Answer 57

𝑸 = 𝒎𝒄∆𝑻
Q: quantity of energy
m: mass of substance
c: specific heat capacity of substance
T: change in temperature

Question 58

Describe movement of kinetic energy in terms of particles

Answer 58

The molecules of a hot object are in constant motion moving back and forwards with vibrational kinetic energy. This kinetic energy gets passed on to the adjacent atoms so that they increase their kinetic energy. The atoms also move further away from each other which produces an expansion in length and width of the object.

Question 59

Describe convection in terms of molecules

Answer 59

As the molecules of a liquid or gas get hotter they move faster. This causes the kinetic energy of the particles to increase and the average distance between the particles increases.
As the particles move further apart there are less of them in a given space. This means that their density decreases.
Less dense liquids and gases float on more dense ones, so a hot liquid or gas will rise. This is the reason we get currents in the ocean and winds in the atmosphere.

Question 60

What emits em radiation

Answer 60

Any object which is hot gives off electromagnetic radiation. The lower the temperature the longer the wavelength of the emitted electromagnetic radiation.

Question 61

Define latent heat

Answer 61

Latent (hidden or unseen) heat is the energy released or absorbed during a change of state. It is the energy needed to change state.

Question 62

Define latent heat of fusion and vaporisation

Answer 62

The heat absorbed when a solid melts is called the latent (hidden or unseen) heat of fusion.
The heat absorbed when a liquid boils is called the latent heat of vaporisation.

Question 63

Latent heat formula

Answer 63

Q=mL
Q: heat energy transferred in joules (J)
m: mass in kg
L: latent heat (J kg^-1)’
Latent heat of fusion formula
Q=mLfusion
Q: heat energy transferred in joules (J)
m: mass in kg
Lfusion: latent heat of fusion (J kg^-1)
Latent heat vaporisation
Q=mLvapour
Q: heat energy transferred in joules (J)
m: mass in kg
Lvapour: latent heat of vaporisation (J kg^-1)

Question 64

Define thermal conductivity

Answer 64

Thermal conductivity describe the ability of materials to conduct heat. It is temperature dependent and is measured in watts per mete per kelvin (W m-1 k-1).

Question 65

Factors that influence thermal conductivity

Answer 65

Nature of the material (the more thermal conductivity the material possess the faster it will conduct heat)
Temperature difference between the two objects (greater temperature difference results in a faster rate of energy transfer)
Thickness of the material (thicker materials require a greater number of collisions between the particles or movement of electrons to transfer energy from one side to the other)
Surface area (increasing the surface area relative to the volume of a system increases the number of particles involved in the transfer process, increasing the rate of conduction).

Question 66

Formula for thermal conductivity

Answer 66

𝑄/𝑡=(𝑘𝐴∆𝑇)/𝑑
Q/t: rate of heat energy transferred (J s^-1)
k: thermal conductivity of the material (W m^-1 K^-1)
A: surface area perpendicular to direction of heat flow (m^2)
∆𝑇: temperature difference across material in kelvin or degrees celsius
d: thickness of the material through which the heat is being transferred (in m)

Question 67

Checklist for hypothesis (What must the hypothesis have)

Answer 67

Is the hypothesis based on information contained in the research? Y/N
Does the hypothesis include the independent and dependent variables? Y/N
Have you worded the hypothesis so that it can be tested in the experiment? Y/N
Have you established design criteria?

Question 68

Golden rule to write a good method

Answer 68

The golden rule to writing a good Method section is to ask yourself whether your reader could replicate your study based on just the information you provided.

Question 69

How should this step be written
use the ruler to hold the ball 1 metre above the surface then drop it while the person observing measures the height of the bounce.

Answer 69

The steps are numbered, in the order someone should do them.
Each step begins on a new line.
3. Hold the ruler vertical on the ground.
4. Hold the ball level with the top of the ruler and in front of it.
5. Position the observer where the ball and the numbers on the ruler can easily be seen or recorded.
6. When everything is ready, drop the ball while the observer looks/records

Question 70

Types of repetition in method

Answer 70

Repetition by doing the experiment again ‘from the start’. Eg after bouncing our ball on a surface, we bounce it again, and again, and again.
Replication where you have multiple copies of the ‘same’ experiment running at the same time. Eg. Testing fertiliser on plants, you will need 3 plants for fertilizer A, 3 plants for fertilizer B, etc. THIS is better if you can!

Question 71

Parts of risk assessment

Answer 71

There’s three parts to a Risk Assessment:
The RISK (aka Hazard) – i.e., what is dangerous in the experiment. There will probably be several risky objects or situations or things that can go wrong.
The INJURY – what injury could this risk cause you. Each risk may have multiple injuries.
The MANAGEMENT – how do we prevent this injury AND/OR what do we do if something goes wrong. There’s many different ways, like use something different, or wear protective clothing, or just be careful.
PRECAUTION

Question 72

Bouncing Ball results

Answer 72

Include:
Title (heading for the table overall)
Headings for columns and rows
Correct number of rows and columns
Units (should be in the headings of the columns, not after each measurement
Averages of results

Question 73

Type of graphs used to depict results

Answer 73

A column graph is used when your data is qualitative (i.e. not in numbers), e.g. fruit, colours, brands, etc.
A line graph is used when your data is quantitative (i.e. measured using numbers), e.g. time, temperature, volume, weight, etc.
Line graph is preferred

Question 74

Features of graph

Answer 74

All graphs must have certain features:
Heading – a name for the graph, which shows what it is all about.
Horizontal axis, also called the X axis– the line across the bottom of the graph. MUST be used for your INDEPENDENT VARIABLE
Vertical axis, or Y Axis – the line up the left side of the graph. This is where you put your dependent variable.
Axis titles – both axes need titles, so we know what they are showing.
Units – both axes should also include the units for whatever you are measuring, usually in brackets after the axis title (cm, kg, N, etc).
Scales – both the X and Y axis need scales. These are the marks and numbers that allow us to put the points in the right places. They must be evenly spaced

Question 75

What does the conclusion include

Answer 75

Address the Aim – i.e. did you achieve your aim? did you find out the thing you wanted to, and if so, what was the answer?
Address the Hypothesis – i.e. Was your hypothesis ‘supported’, or ‘refuted’ (found to be incorrect)