| Syllabus | Alternate Universe Cambridge 0625 |
| Subject | Physics (0625) Core |
| Paper | 0625/33/O/N/25 · Paper 3, Variant 3 |
| Also listed as | 0625_w25_qp_33 · 0625_w25_ms_33 |
| Session | October/November 2025 |
| Questions | 10, multiple choice, with answers and explanations |
| Cost | Free |
0625/33/O/N/25 answer key
Preview the first questions
Question 1
A stone falls freely from rest. Its speed increases linearly from $0$ to $33\ \text{m/s}$ in a time of $3.4\ \text{s}$. What is the distance the stone falls during this $3.4\ \text{s}$?
- $56\ \text{m}$
- $112\ \text{m}$
- $28\ \text{m}$
- $9.7\ \text{m}$
Show the answer and explanation
Correct answer: A
Step 1: On a speed-time graph, the distance travelled is the area below the line. For uniform acceleration from rest, this is a triangle. Step 2: Area $= \tfrac{1}{2} \times 3.4 \times 33 \approx 56\ \text{m}$.
Question 2
A truck does $5800\ \text{J}$ of work in $7.4\ \text{s}$ when lifting a rock. What is the average power developed by the truck during this time?
- $780\ \text{W}$
- $43\,000\ \text{W}$
- $0.0013\ \text{W}$
- $1.3\ \text{W}$
Show the answer and explanation
Correct answer: A
Step 1: Power = work done / time, so $P = W/t$. Step 2: $P = 5800 / 7.4 \approx 784\ \text{W} \approx 780\ \text{W}$.
Question 3
A plastic object has a density of $0.905\ \text{g/cm}^3$. It is placed in sea water (density $1.030\ \text{g/cm}^3$) and then in baby oil (density $0.815\ \text{g/cm}^3$). In which of these liquids does the plastic object float?
- in sea water only
- in baby oil only
- in both liquids
- in neither liquid
Show the answer and explanation
Correct answer: A
Step 1: An object floats only if its density is less than the liquid's density. Step 2: Plastic ($0.905$) is less dense than sea water ($1.030$), so it floats in sea water. Step 3: Plastic ($0.905$) is denser than baby oil ($0.815$), so it sinks in baby oil.
Worked answers: questions 4 to 10
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Question 4 · Answer A
Step 1: When a pure substance changes state, its temperature stays constant. Step 2: The first plateau (at $60\ ^\circ\text{C}$) is the melting point. Step 3: The second plateau (at $140\ ^\circ\text{C}$), which appears after the liquid stage, is the boiling point.
Question 5 · Answer A
Step 1: Wave equation $v = f\lambda$, so $\lambda = v/f$. Step 2: $\lambda = \frac{3.0 \times 10^8}{6.0 \times 10^{14}} = 0.5 \times 10^{-6} = 5.0 \times 10^{-7}\ \text{m}$.
Question 6 · Answer A
Step 1: The line through the centre of the lens, perpendicular to the lens, is the principal axis. Step 2: Focal length is a distance along this axis, not a line. Normal applies to a surface (such as a flat mirror), not the lens as a whole. Wavefronts are surfaces of constant phase, drawn perpendicular to the rays.
Question 7 · Answer A
Step 1: Ohm's law: $R = V / I$. Step 2: $R = 6.0 / 0.25 = 24\ \Omega$.
Question 8 · Answer A
Step 1: For a given power $P = VI$, raising $V$ lowers $I$ in the cables. Step 2: Cable power loss is $I^2 R$, which falls sharply with smaller current. Step 3: Less power is lost as heat in the cables.
Question 9 · Answer A
Step 1: Alpha is stopped by a sheet of paper, so Q is alpha. Step 2: Beta passes paper but is stopped by a few mm of aluminium, so P is beta. Step 3: Gamma passes both paper and aluminium, so R is gamma.
Question 10 · Answer A
Step 1: A day is one spin of the Earth on its axis. Step 2: A year is one full orbit of the Earth around the Sun. Step 3: A month is one full orbit of the Moon around the Earth.