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1A]  As sound is produced , the molecules around the speaker vibrates which then cause air molecules that are further away to vibrate as well causing them to vibrate and eventually producing a sound wave. 👌 This also creates region of compression and rarefaction

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1bi] It means that the number of waves (20,000) produced in a second which can be heard by a human is as large as 20 kHz. 👌

1bii] v= f x ^
^ = 340 / 20 000
=0.017m ❌ 17m (longest wavelength)

2b]  a=v-u / t
= 45-20/60
= 0.417 . m/s^2 👌

2c] F=ma
= 1200 x 5/12
= 500 N 👌

3a] W= mass x g
mass= 2.6 / 10
=0.26 kg 👌

3b] d= m/v
mass = 0.80 x 250
= 200g
= 0.20kg 👌

4b] 0.20 x 50 = 0.60 x w
10N = 0.60 x w
w = 10 x 0.60
=6 N ❌

4c]

5a]  gravitational potential energy
= mgh
= 1.6 x 10 x 1.0
=16 J
KE = 1/2 mv^2
16 = 1/2 x1.6 x v^2
V^2=20
V= 4.47m/s 👌

b]

6a] Sterilisation of Dental equipment
wireless networks, (UV is too ionising to be used for wireless networks. Only radio waves and low frequency microwaves are used)

6b] common property: they are transverse waves 👍

different: they have different frequencies 👍

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when sound is played, the speaker drum vibrates. the air particles next to it vibrates, collides and transfers energy to the neighbouring air particles 👌 which sets up and alternating series of compression and rarefactions in the air. 👌 it travels through the air as longitudinal waves to all parts of the room

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The particles cone of the loudspeaker will vibrate and push and pull the neighbouring air molecules then travels as a longitudinal waves. The vibration causes a displacement in the particles around it causing regions of rarefactions and compressions to be produced 👌

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b) Frequency of 20 khz is the audible frequency range for a human where pitch can be heard.

Note: Answer is not checking about the audible hearing range of human but what does frequency of 20 kHz is interpreted as 20000 waves are produced in 1 second.

c) v = f x wavelength
340 = 20000 x wavelength
wavelength = 0.017 m ❌  17m (longest wavelength)

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1) Sound is produced when the speaker vibrates, this causes the neighbouring air molecules to vibrate as well.👌 The vibration passes from one layer of air to the next and  Regions of compression and rarefaction is produced. 👌

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It means the highest pitch a human can hear is 20000 hertz. ❌

Answer: 20000 waves are produced in 1 second.

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20kHz is 20000 waves produced per second 👌

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it means that the highest pitch that humans are able to hear is 20kHz❌

Answer: 20000 waves are produced in 1 second.

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speed = frequency x wavelength
wavelength = speed/ frequency
wavelength = 340/20
=17m 👌

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b) 45 - 20 / 60
= 0.41666
= O.417 m/s^2 (3.SF) 👌

C) F = ma
F = 1200 (0.416666)
= 500N 👌

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v=fλ
λ=v/f
λ=340/f
λ=340/ 20
λ=17m     👌

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2b)(45-20)/60
=0.41666
=0.417 m/s^2(3sf) 👌
2c) FR=ma
resultant force = 1200kg x 0.416666 = 500N 👌

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W=mg
weight = m x 10
2.6= m x 10
m= 0.26kg 👌

b) mass of methanol= density x volume
mass= 0.8 x 250
= 200g
=0.2kg 👌

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25 m/s ❌
( 0.417 m/s)

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2b)25/60= 0.417m/s^2 👌
2c) f=ma
=1200 x 0.41667 = 500 N 👌

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500.4 N Round off to 500N
( 500 N)

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A)  W = mg
2.6 = m(10)
m = 0.26 kg 👌

b) density = m /v
0.8 = m / 250
m = 312.5 g
= 0.3125 kg ❌ (0.2 kg)

Note: mass = density x volume

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b) 0.20 x 50 =0.60 x W
10 N = 0.60W
W = 6 N ❌

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2.6/10=0.26kg 👌

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a) PE = mgh
= (1.6)(10)(1.0)
= 16J
KE=1/2MV^2
16=1/2 (1.6) V^2
V^ = 20
V = 4.4721
= 4.47m/s (3.sf) 👌

b)

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mass= density x volume
=0.80x250=200g
=0.2kg 👌

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4b)total moments= force x perpendicular distance
anticlockwise= clockwise
0.40 x 70 + 0.2 x 50
=38Nm 👌
4c) sum of CW = sum of anti clockwise
38Nm = 0.8 x force at b
b = 38/ 0.8
= 47.5N👌

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a) ultraviolet : sunbeds/ sterilization of medical equipment
microwaves : microwave oven cooking of food /satellite television  (Note: microwave oven is a device and not a purpose of microwave. The purpose is to cook food)

b) common property : They are transverse waves 👍

different property: microwave have a lower frequency than ultraviolet.
👍

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a) The black heat sink is made of metal which is  a good absorber conductor of heat, which allows heat to go to the heat sink  rather than the computer chip. 👍

2nd feature: ???
The heat sink in black in colour which is a good emitter of heat which helps the heat sink to radiate heat faster.

b) as the heat sink gains heat, it gains kinetic energy and thermal energy. Molecules in the heat sink start to vibrate about fixed position more vigorously and the average spacing between them increases 👍

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total moments

= 70x0.8+50x0.2

=66

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Pd = RI
= 3(1.5)
=4.5 V  👍

b) 12 - 4.5 = 7.5 v
R=V/I
6.0=7.5 /I
I = 0.8 A ❌

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a) P = F/A
=300/20 👍
=20N/CM^2 (typo error)

B) 15 N/cm2 (pressure inside the piston is same throughout)

(c) Valve A will open and oil flows from reservoir into Piston P, Valve B will close, Piston Q remains unchanged.

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(b) Inverted and enlarged  ✔✔
(c) projector  👍

(d) The image will be dimmer. Reason: Less light from the object would pass through the lens to form the image.

(ei) critical angle = sin90/sin40
= 1.5557
=1.56 (3.sf) ❌ They want the critical angle, not the refractive index
1.54=sin90/sini
critical angle= 40.492=40.5 (1dp) 👍👍

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(a) p=v^2 / R
100=240^2/R
R = 576 ohms  👍👍

(b) 100W = 0.1kwh
cost=0.1 x 5 x 0.24
=$0.12 ✔✔

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GPE= mgh=1.6x 10x 1=16
KE = 1/2 mv^2=16
v^2= 8/1.6
=5
v=2.24m/s (3sf) ❌

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5a) by using principal of conservation of energy, gpe = ke
gpe=mgh
= 1.6 x 10 x 1
=16
KE = 1/2 mv^2
16= 1/2  x 1.6 x v^2
v^2 =20
v= 4.47m/s 👌
b)

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ai) used in tanning beds to help people achieve suntan
aii)microwave oven to cook food
b) common property: they are both transverse waves 👍
different property: they have different frequency 👍

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a) one feature would be the metal fins. since metal is a good conducter of heater it would conduct the heat of the computer chip preventing it from over heating
another feature would be that the metal fins are black as black is a good emitter of heat through radiation

The metal fins have a large combined surface area , that allows heat to be radiated more quickly (radiation depends on exposed area) and heat lost faster through convection current due to more greater surface area of contact.

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7a] The heat sink is painted black and black surfaces are better absorbers and emitter (note: heat sink needs to help chip dissipate heat) of infrared radiation which cause thermal energy to be transferred easily away from the chip.

The heat sink is also made out of metal. Metal has a shiny surface which caused heat to be reflected easily. Metals are good thermal conductors and heat produced by the chip is conducted away quickly.

7b] As the heat sink gains heat, they vibrate about their fixed positions more vigorously and their molecules would be arranged slightly further apart. 👍👍

8.

9a] V=IR
= 1.5 x 3.-
=4.5 V 👍

b] potential difference at z
=12- 4.5 = 7.5 V
I of z = 7.5 / 6.0
=1.25 A. 👍

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both are trans verse waves/ 👍
ii) diff wavelengths and frequencies 👍

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Black metal fins help with thermal energy transferrence transfer as it is made of metal hence it is a good conductor of heat, this means heat energy is conducted away quickly from the chip and prevents any over heating.

good conductors mean good The black matt paint of the fins allows the heat sink to be good absorber and emitter of radiation and so heat energy can be radiated away from the chip quickly.

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as idk

As the temperature rises, the molecules in the heat sink vibrate more vigorously.
The average spacing between the molecules increases.

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ai) P=F/A= 300/20=15N/cm^2 👍
aii)15N/cm^2 👍
aiii)F=AxP=400x15=6000
bi)volume=basexheight=20x5=100cm^3
bii) height= volume/base=100/400=0.25cm 👍👍
c)nothing will happen to valve a, (OPEN)  valve b will close  👍 and piston q will move down ❌
Nothing will happen to Piston Q

d) this is because the particles in air are much further apart which will be compressed when pressure is applied unlike oil which particles are closely packed allowing it to move but making it hard to be compressed

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a) V=IR=1.5x3=4.5 V 👍
b) I=V/R= 4.5/6=0.75 ❌ 1.25A

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10 a] P= F / A = 300 / 20 = 15N cm^2 👍

10(b) 15 N/cm2 (pressure inside the piston is same throughout)

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Molecules in the sink gain heat and kinetic energy, they start vibrating in their spots. Hence the spaces between the molecules increase. 👍

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15n/cm2

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ai) sunbeds (UV is used to help people get tanned in a sunbed)

Note: Sunbed is a device that produces the ray so cannot be considered usage of the UV rays.

aii)Microwaves are used to cook food
b) common property:  they are both transverse waves. 👍
different property: they have different frequencies. 👍

7a) First feature :This is because the heat sink is made out of a metal.painted black colour Metals Black surfaces are good absorbers and emitters of radiation compared to bright/shiny sufaces which helps the metal sink to radiate heat faster than non metals and allows it to cool faster.

Second feature: The heat sink is made of metal, which is a good conductor of heat.  This allows heat to be conducted away from the chip faster by the heat sink to prevent any overheating.

b) Once the heat sink absorbed radiation, it gains heat which causes a gain in kinetic energy. The molecules

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ai) pressure= force/area
pressure= 300N/20cm^2
= 15N/cm^2  👍
ii) 15N/cm^2  👍
iii)force= area x pressure
force= 400 x 15
= 6000 N  👍
bi) volume= 20 x 5
= 100cm^2 3
bii) volume= base area x height
height=volume/ base area
= 100/400 = 0.25cm
C) nothing will happen to all of them. This is because when x is lifted up, they will all go back to their original positions and values and hence there will be no change.❌ Valve A will open and oil flows from reservoir into Piston P, Valve B will close, Piston Q remains unchanged.

d) This is because air does not have a fixed volume and hence when the hydraullic pressed is pushed down, the air from the surrounding atmosphere might make it harder to press down due to air particles being hard to compress.

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15n + (pressure of piston q)????
= 15 N/cm2 (pressure inside the piston is same throughout)

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(400xd= 100
d= 100/400
= 0.25cm 👍

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10aiii] Pressure= F/A
Force= Pressure x area
=400 x 15
= 6000N 👍

b] volume= base area  x height
= 20 x 5
= 100cm^3 👍
bii]
volume = base area x height
height= base area / volume
= 100 / 400
=0.25 cm 👍

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b) upright and enlarged 👌 (Note: cannot be upright since the image is reverse that of the object)-- enlarged and real *👍

c) magnifying glass?? ❌
Note: Magnifying glass produces virtual image. Hence the correct answer should be "projector"

d) there would be no change ❌ as the light rays only passes through the bottom half to reflect. (Note: The size and focus of the image remains the same. However, due to lesser light rays forming the image, it becomes dimmer)

e) sin c= 1/n
c=sin^-1(1/1.54)
=40.5 degrees ( 3 sf ) ✔✔

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11b

Image is larger (please use "magnified or enlarged"), inverted and real and further

Note: Further is not an image property.

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11 b enlarged and inverted ✔✔

11c microscope ❌ projector

11d the image produced would be smaller ❌ Image would be dimmer. Reason: Less light from the object would pass through the lens

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real and inverted ✔✔
c) magnifying glass ❌
Note: Magnifying glass produces virtual image. Hence the correct answer should be "projector"

d) the image will now become blured. This is because when the top half is blocked, one some of the rays are unable to reach to the point👍 . Hence, the image will look blur
Note: blurred object happens because the light rays did not focus well. If less amount of light forming image, the image will be "dimmed" .

ei) n=1/sin c
= 1/1.54
=40.5(3sf)  ✔✔
ii)

Note

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11ei] sin c=1/n
c=sin^-1 [1/1.54]
=40.49
=40.5 degress ✔

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spectacles ❌ projector

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12 a i] P=v^2 / R
R= v^2/ P
=57600V / 100 W
= 5760  ohm ✔✔ ( careless calculation mistake)

12aii] cost of lamp 1 day
=0.24 x 5 x 100
=$120 ❌ $0.12

(Note: 100 W = 0.1 kW so the amount of energy usage should be 5x0.1 = 0.5 kWh so the cost = 0.24 x 0.5 = $0.12)

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image produced will be darker dimmer
Reason: Less light from the object would pass through the partially blocked lens.

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i) P=IV
100= I(240)
I=100/240
=5/12
R=V/I
R= 240/5/12
=576ohm ✔✔

aii) (Note: 100 W = 0.1 kW so the amount of energy usage should be 5x0.1 = 0.5 kWh so the cost = 0.24 x 0.5 = $0.12)

12b) This is so that the wires do not recieve any excess current from the wire to prevent overheating.❌ (overheating is NOT possible if there is no short circuit)

When the wires are switch, the resistance of the wires are also different which may result in a surge of current flowing through the wires which might melt the protective layer of the wire and might cause a short circuit if the exposed wire comes into contact with the other wires. ❌

This is because wire A has a switch connected to it.
So when the switch is open, the appliance will be disconnected from the high voltage live wire. Thus preventing the possibility of electric shock to the user.

c) wire B. ❌ Wire C (this is the earth wire). Under normal operation, no current should flow through earth wire.

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ai) R=V/I
= 240/100=2.4 ❌ idk how to find the symbol but yes

(Note: The 100W is power. So you can use the formula P=V^2/R --> R = V^2/P = 240 ²/100 = 576 ohm

aii)(Note: 100 W = 0.1 kW so the amount of energy usage should be 5x0.1 = 0.5 kWh so the cost = 0.24 x 0.5 = $0.12)

b) this is because when the switch is off, it will cause the circuit to open and there would be no more current flowing towards the bulb anymore. unlike when the ( I realised I read the question wrong ) nvrm ✔✔

Update: This is because wire A has a switch connected to it. So when the switch is open, the appliance will be disconnected from the high voltage live wire. Thus preventing the possibility of electric shock to the user.

c) wire b ❌ Wire C (this wire is the earth wire) there should not be any current flowing under normal operating conditions.

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1.54= 1/sin(c)
c= sin-1(1/1.54)
= 40.5 ✔✔

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a)  i]  100= 240(240)/R
R= 240(240)/100
= 576 ohm ✔✔

ii] $1.20 ❌(Note: 100 W = 0.1 kW so the amount of energy usage should be 5x0.1 = 0.5 kWh) Hence the cost will work out to be $0.12

b) That way there wont be overheating of cables as if it was connected to the live terminal, it would carry the current from the terminal to the bulb but with the wire a being connected, it will carry through wire A and then to wire b to light up the bulb.❌

Note: Overheating is due to electrical fault e.g. frayed live wires touching neutral wire or casing.

This is because wire A has a switch connected to it.
So when the switch is open, the appliance will be disconnected from the high voltage live wire. Thus preventing the possibility of electric shock to the user.

c) Neutral Wire. ❌ Wire C (earth wire) since under normal operation, the casing should NOT be live.

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12 b there are many plugs connected to wire a if  wire A is connected to the live terminal it would reduce the current  This is because wire A has a switch connected to it.
So when the switch is open, the appliance will be disconnected from the high voltage live wire. Thus preventing the possibility of electric shock to the user.

12c  wire c ✔
12 d  not sure