Official Answer Key

Q	Ans	Q	Ans	Q	Ans	Q	Ans
1	B	11	A	21	D	31	C
2	D	12	D	22	D	32	A
3	D	13	D	23	C	33	C
4	B	14	B	24	B	34	A
5	A	15	D	25	B	35	C
6	D	16	A	26	A	36	B
7	D	17	B	27	B	37	D
8	C	18	C	28	B	38	C
9	A	19	C	29	B	39	D
10	C	20	D	30	A	40	C

Detailed Explanations

Q1 — Correct answer: B

Vector quantities have magnitude and direction.

Option B contains only vectors:

• momentum
• gravitational field strength
• displacement

Why others are wrong:

• A: mass and distance are scalars.
• C: energy is scalar, although force and velocity are vectors.
• D: time and speed are scalars, although acceleration is a vector.

Q2 — Correct answer: D

The distance-time graph becomes less steep with time and then becomes horizontal.

On a distance-time graph:

• gradient = speed
• decreasing gradient = slowing down
• horizontal section = object has stopped

So the object is a train braking to a halt as it stops at a station.

Why others are wrong:

• A: a ball thrown upwards and falling back would not have distance from start simply increasing then becoming flat.
• B: speeding up would give an increasing gradient, not decreasing.
• C: a dropped rock speeds up, so the gradient should increase.

Q3 — Correct answer: D

Terminal velocity is reached when:

weight = air resistance

For a heavy coin falling a short distance, air resistance does not have enough time to build up until it equals weight.

So throughout the short fall:

weight > air resistance

Therefore, it does not reach terminal velocity.

Why others are wrong:

• A: not hitting the ground does not explain terminal velocity.
• B: if weight equalled air resistance, terminal velocity would have been reached.
• C: weight does not increase as air resistance increases; weight is almost constant near Earth.

Q4 — Correct answer: B

On a speed-time graph:

area under graph = distance travelled

Area X is the distance travelled during the driver’s reaction time, before braking begins.

So:

• Student 1 is correct: X = thinking distance.
• Student 2 is wrong: Y is only the braking distance, not the full stopping distance.
• Student 3 is correct: X + Y = stopping distance.

Therefore, students 1 and 3 are correct.

Why others are wrong:

• A: includes student 2, who is wrong.
• C: misses student 3.
• D: student 2 alone is wrong.

Q5 — Correct answer: A

The limit of proportionality is the point where the graph stops being a straight line.

Before this point:

load is proportional to extension.

At point A, the graph begins to curve away from the straight-line relationship.

Why others are wrong:

• B, C and D: these are after proportionality has already broken down.

Q6 — Correct answer: D

There is no atmosphere on the Moon, so there is no air resistance.

In a vacuum/no atmosphere, all objects fall with the same acceleration regardless of mass.

So the two spheres hit the ground together.

Why others are wrong:

• A: larger mass does not mean smaller acceleration.
• B: larger mass does not make it hit first without air resistance.
• C: smaller mass does not mean smaller acceleration.

Q7 — Correct answer: D

Given:

weight = 1.2 N
g = 9.8 N/kg

Mass:

mass = weight / g
mass = 1.2 / 9.8
mass = 0.122 kg
mass = 122 g approximately

Volume of rock:

147 – 100 = 47 cm³

Density:

density = mass / volume
density = 122 / 47
density = 2.6 g/cm³

So the answer is D.

Why others are wrong:

• A: 1.2 / 47 gives 0.026 N/cm³, but that is not density in g/cm³.
• B: much too low; likely uses volume/mass instead.
• C: wrong unit and wrong value.

Q8 — Correct answer: C

Kinetic energy:

KE = 1/2 mv²

Given:

m = 20 kg
v = 6.0 m/s

KE = 1/2 × 20 × 6²
KE = 10 × 36
KE = 360 J

Answer C.

Why others are wrong:

• A: uses incomplete calculation.
• B: likely uses mv instead of 1/2mv².
• D: forgets the 1/2.

Q9 — Correct answer: A

Nuclear fuel does not release carbon dioxide during electricity generation, which is an advantage.

However, it produces radioactive waste, which is a major disadvantage.

Answer A.

Why others are wrong:

• B: “only works in some weather conditions” applies to sources like solar/wind, not nuclear.
• C: nuclear fuel is not renewable; uranium is finite.
• D: both parts are wrong for nuclear fuel.

Q10 — Correct answer: C

Work done is:

force × distance moved in the direction of the force

The unit of work done is the joule, J.

Answer C.

Why others are wrong:

• A and B: energy transferred per unit time is power, not work done.
• D: N/m is not the unit of work; work is N m, which equals J.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

Q11 — Correct answer: A

The hammer force on the nail and the force transferred by the nail to the wood are equal in size.

So:

FW = FH

Pressure depends on area:

pressure = force / area

The pointed end of the nail has a much smaller area than the hammer end, so the pressure on the wood is greater.

So:

pw > pH

Answer A.

Why others are wrong:

• B: pressure on the wood is not smaller; the nail tip has smaller area.
• C and D: force is not greater; the force is transferred through the nail.

Q12 — Correct answer: D

Liquid pressure is:

pressure = density × g × depth

Pressure increases when:

• depth increases
• density increases

So both must increase.

Answer D.

Why others are wrong:

• A: both decrease, so pressure decreases.
• B: density increases but depth decreases.
• C: depth increases but density decreases.

Q13 — Correct answer: D

The air is heated and the piston moves to the right.

Heating makes the particles move faster, but the gas expands, so the particles become more spread out.

The quantity that decreases is:

number of collisions made by air particles with the piston in one second

Why others are wrong:

• A: average force per collision does not decrease; faster particles tend to hit harder.
• B: average speed increases when temperature increases.
• C: mass of air remains the same because no air escapes.

Q14 — Correct answer: B

Temperature remains constant, so Boyle’s law applies:

P1V1 = P2V2

Given:

P1 = 120 kPa
V1 = 150 cm³
V2 = 100 cm³

P2 = 120 × 150 / 100
P2 = 180 kPa

Answer B.

Why others are wrong:

• A: pressure should increase because volume decreases.
• C and D: wrong units/scale; answer should remain in kPa, not jump to thousands of kPa.

Q15 — Correct answer: D

From the diagram:

• W: liquid → gas = boiling
• X: gas → liquid = condensation
• Y: solid → liquid = melting
• Z: liquid → solid = freezing

So the answer is D.

Why others are wrong:

• A: W and X are reversed, and Y/Z are reversed.
• B: W and X are reversed.
• C: W and X are correct, but Y and Z are reversed.

Q16 — Correct answer: A

The hotplate and metal pan are touching.

Thermal energy transfer through direct contact in a solid is conduction.

Answer A.

Why others are wrong:

• B: convection happens in liquids and gases due to bulk movement.
• C: diffraction is bending/spreading of waves.
• D: refraction is bending of waves when speed changes.

Q17 — Correct answer: B

When water is heated:

• it expands
• its density decreases
• less dense water rises upwards

So the heated water has lower density and moves upwards.

Answer B.

Why others are wrong:

• A: density decreases, but there is movement.
• C: density does not increase.
• D: movement upwards is correct, but density does not increase.

Q18 — Correct answer: C

A rarefaction is a region of lower pressure.

On the graph, point Q is below atmospheric pressure, so Q represents a rarefaction.

Wavelength is the distance between two points in the same phase, such as compression to compression or rarefaction to rarefaction.

The wavelength is shown by X.

Answer C.

Why others are wrong:

• A and B: P is a compression/high-pressure region, not a rarefaction.
• D: Q is a rarefaction, but Y is not the wavelength.

Q19 — Correct answer: C

From the graph:

amplitude = 2.0 cm

The question says the numerical value of wavelength equals the numerical value of amplitude.

So:

wavelength = 2.0 cm

From the graph, the period is 0.5 s.

Wave speed:

speed = wavelength / period
speed = 2.0 / 0.5
speed = 4.0 cm/s

Answer C.

Why others are wrong:

• A: uses too large a period.
• B: likely uses 1.0 s as the period.
• D: likely uses double the correct frequency or wavelength.

Q20 — Correct answer: D

When a water wave moves from deep water to shallow water:

• speed decreases
• frequency remains constant
• wavelength decreases because v = fλ

Answer D.

Why others are wrong:

• A and B: speed does not increase in shallow water.
• C: wavelength does not increase when speed decreases and frequency stays constant.

Q21 — Correct answer: D

The 40° shown is the angle between the ray and the mirror surface.

Angle of incidence is measured from the normal, not from the mirror.

Normal is 90° to the mirror.

So:

angle of incidence = 90° – 40° = 50°

For reflection:

angle of incidence = angle of reflection

So both are 50°.

Answer D.

Why others are wrong:

• A: uses the angle with the mirror surface as the angle of incidence.
• B and C: one of the angles is incorrectly measured from the mirror instead of the normal.

Q22 — Correct answer: D

When the angle of incidence equals the critical angle, the refracted ray travels along the boundary.

So the ray should travel along the glass-air surface.

Diagram D shows this.

Why others are wrong:

• A: shows refraction into air at an angle, not along the surface.
• B: does not show the correct critical-angle behaviour.
• C: shows total internal reflection, which happens when the angle is greater than the critical angle, not equal to it.

Q23 — Correct answer: C

The object is between a converging lens and its principal focus, so the image is virtual and magnified.

From the scale in the diagram:

focal length f = 3 cm
object distance u = 2 cm

Using the lens relation for a virtual image:

1/f = 1/u – 1/v

1/3 = 1/2 – 1/v
1/v = 1/2 – 1/3
1/v = 1/6
v = 6 cm

Magnification:

magnification = image distance / object distance
magnification = 6 / 2
magnification = 3.0

Answer C.

Why others are wrong:

• A: no magnification; not correct for object inside focal length.
• B: too small.
• D: too large; it uses image distance alone instead of v/u.

Q24 — Correct answer: B

Red light has a lower frequency than violet light.

In the visible spectrum:

red has the longest wavelength and lowest frequency
violet has the shortest wavelength and highest frequency

Answer B.

Why others are wrong:

• A: violet is deviated more by a prism than red.
• C: red has a longer wavelength, not shorter.
• D: all electromagnetic waves travel at the same speed in a vacuum.

Q25 — Correct answer: B

Ultrasound is used in prenatal scanning to form images of a developing baby.

Answer B.

Why others are wrong:

• A: optical fibre communication uses light, not ultrasound.
• C: photography uses visible light.
• D: telephone communication mainly uses electrical/electromagnetic signals, not ultrasound.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

Q26 — Correct answer: A

For the sea bed:

time = 1.0 s

The sound travels down and back, so:

depth = speed × time / 2
depth = 1500 × 1.0 / 2
depth = 750 m

For the whale:

time = 0.60 s

distance from ship to whale:

= 1500 × 0.60 / 2
= 450 m

Distance of whale above sea bed:

750 – 450 = 300 m

Answer A.

Why others are wrong:

• B: 450 m is the distance from ship to whale, not whale above sea bed.
• C: wrong subtraction.
• D: gives the sea depth, not the whale’s height above the sea bed.

Q27 — Correct answer: B

Ultrasound is sound with frequency greater than 20 kHz.

Sound waves are longitudinal.

So ultrasound is:

longitudinal, greater than 20 kHz

Answer B.

Why others are wrong:

• A: frequency should be greater than 20 kHz, not smaller.
• C: sound is not transverse and frequency is wrong.
• D: frequency is correct but wave type is wrong.

Q28 — Correct answer: B

Electromotive force, e.m.f., is defined as:

work done by a source in moving unit charge around a complete circuit.

Its unit is the volt, V.

Answer B.

Why others are wrong:

• A: e.m.f. is correct, but unit is not newton.
• C: potential difference is energy transferred per unit charge between two points, not by the source around the complete circuit.
• D: volt is the correct unit, but the quantity described is e.m.f., not p.d.

Q29 — Correct answer: B

The two 6.0 Ω resistors at the bottom are in parallel.

Equivalent resistance:

1/R = 1/6 + 1/6
1/R = 2/6
R = 3.0 Ω

Now the circuit has:

• 3.0 Ω left resistor
• 3.0 Ω equivalent bottom section
• 6.0 Ω right resistor

These are in series.

Total resistance:

3 + 3 + 6 = 12 Ω

Current:

I = V / R
I = 6.0 / 12
I = 0.50 A

The voltmeter is across the right-hand 6.0 Ω resistor.

Voltage:

V = IR
V = 0.50 × 6.0
V = 3.0 V

Answer B.

Why others are wrong:

• A: too small; would imply only 1.0 V across the 6 Ω resistor.
• C: incorrect sharing of voltage.
• D: would mean the right-hand resistor gets the full supply voltage, but other resistors are in series with it.

Q30 — Correct answer: A

In a series circuit, the same current flows through both resistors.

For each resistor:

V = IR

So:

V1 = IR1
V2 = IR2

Therefore:

V1 / V2 = R1 / R2

Answer A.

Why others are wrong:

• B: inverted ratio.
• C and D: voltage ratio is not the square of the resistance ratio.

Q31 — Correct answer: C

Energy transferred electrically:

E = I²Rt

Given:

I = 1.5 A
R = 4.0 Ω
t = 1.0 minute = 60 s

E = 1.5² × 4.0 × 60
E = 2.25 × 4.0 × 60
E = 9.0 × 60
E = 540 J

Answer C.

Why others are wrong:

• A: uses only V = IR or a partial calculation.
• B: likely uses IVt with wrong voltage.
• D: too large; incorrect squaring/multiplication.

Q32 — Correct answer: A

Initially, the plane of the coil is perpendicular to the magnetic field.

At this position, magnetic flux through the coil is maximum, but the rate of change of flux is zero.

So induced e.m.f. starts at zero.

As the coil rotates, the rate of change of flux increases, so e.m.f. increases to a maximum at 90°.

At 180°, the flux is again maximum in the opposite direction, but momentarily its rate of change is zero again.

So the e.m.f.:

starts at zero → rises → falls back to zero over 180°

Answer A.

Why others are wrong:

• B: starts with maximum e.m.f., but it should start at zero.
• C: changes direction within the first 180°, which is not shown for this half-turn.
• D: suggests a straight-line decrease, but induced e.m.f. varies smoothly, not linearly.

Q33 — Correct answer: C

Temporary magnets become magnetised only when placed in a magnetic field.

1. Transformer core: temporary magnet, usually soft iron.
2. Compass needle: permanent magnet.
3. Iron filings: temporary induced magnets when showing field patterns.

So the temporary magnets are 1 and 3 only.

Answer C.

Why others are wrong:

• A: includes compass needle, which is permanent.
• B: includes compass needle and misses iron filings.
• D: includes compass needle and misses transformer core.

Q34 — Correct answer: A

The speed of rotation of a d.c. motor depends on the strength of the turning effect.

The turning effect increases when:

• magnetic field strength increases
• current increases
• number of turns on the coil increases

So all three suggestions are correct.

Answer A.

Why others are wrong:

• B, C and D: each leaves out one factor that affects motor rotation.

Q35 — Correct answer: C

A transformer works by electromagnetic induction.

An alternating current in the primary coil produces a changing magnetic field in the iron core.

That changing magnetic field induces an alternating p.d. in the secondary coil.

Answer C.

Why others are wrong:

• A: the secondary current is not d.c.; transformers require a.c.
• B: more secondary turns means higher voltage, but lower current for the same power.
• D: current does not flow through the iron core from primary to secondary.

Q36 — Correct answer: B

The beta-particle is negatively charged and is deflected downwards in the electric field.

An alpha-particle is positively charged, so it is deflected in the opposite direction: upwards.

However, an alpha-particle has much greater mass than a beta-particle, so at the same speed it is deflected much less.

Path B shows a slight upward deflection.

Why others are wrong:

• A: upward direction is correct, but deflection is too large.
• C: shows no deflection, but alpha particles are charged.
• D: shows deflection in the same direction as beta, but alpha has opposite charge.

Q37 — Correct answer: D

The nucleus contains protons and neutrons.

• Protons are positive.
• Neutrons are neutral.
• So the nucleus is positive overall.

Electrons are negatively charged.

Answer D.

Why others are wrong:

• A: reverses the charges.
• B: nucleus is not neutral in this context.
• C: both charges are wrong.

Q38 — Correct answer: C

The count rate becomes 1/16 of the initial value.

Each half-life halves the count rate:

After 1 half-life: 1/2
After 2 half-lives: 1/4
After 3 half-lives: 1/8
After 4 half-lives: 1/16

So 4 half-lives pass.

Each half-life = 6000 years

Time = 4 × 6000
Time = 24 000 years

Answer C.

Why others are wrong:

• A: only one half-life.
• B: three half-lives gives 1/8, not 1/16.
• D: wrongly multiplies 6000 by 16.

Q39 — Correct answer: D

Light from the Sun takes about 8 minutes 20 seconds to reach Earth.

8 minutes 20 seconds = 8 × 60 + 20
= 480 + 20
= 500 s

Answer D.

Why others are wrong:

• A, B and C: all are far too short for light to travel from the Sun to Earth.

Q40 — Correct answer: C

The asteroid belt is located between Mars and Jupiter.

Answer C.

Why others are wrong:

• A: between the Sun and Mercury is not the asteroid belt.
• B: between Venus and Earth is not the asteroid belt.
• D: between Uranus and Neptune is far beyond the main asteroid belt.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.