Free Interview Resources
Free practice questions, preparation advice, and expert insights for Physics interviews at Imperial College London.
Real Physics interview questions in the style Imperial College London asks. Try answering each one aloud before you reveal the hint.
A ball is thrown at speed v from the ground at angle theta to the horizontal. Without a calculator, derive an expression for its range and show for which angle the range is greatest.
Problem-Solving
Hint
Split into horizontal and vertical motion, find the time of flight from the vertical component, then substitute. Recognise the sin(2*theta) structure to argue the maximum is at 45 degrees.
Estimate the number of piano tuners in London using only quantities you can reason about. Talk me through each assumption as you make it.
Problem-Solving
Hint
A Fermi estimate: population, pianos per household, tuning frequency, and one tuner's throughput per year. Imperial cares about the transparency and reasonableness of each step, not the final number.
A block of mass m sits on a frictionless incline of angle theta connected over a pulley to a hanging mass M. Find the acceleration, then check the limiting cases theta -> 0 and M >> m.
Problem-Solving
Hint
Write Newton's second law along the string for each mass and eliminate the tension. Then substitute the extreme values and confirm the result behaves physically.
Evaluate the integral of x times e to the minus x from 0 to infinity, without a calculator, and explain what physical quantity such an integral might represent.
Problem-Solving
Hint
Integrate by parts once; the boundary term vanishes at both limits, leaving the value 1. Connect it to an expectation value or a mean lifetime for an exponentially decaying distribution.
A uniform ladder rests against a smooth wall on a rough floor. Derive the minimum coefficient of friction that stops it slipping in terms of the angle it makes with the floor.
Problem-Solving
Hint
Take moments about the base to relate the wall reaction to the weight, then balance horizontal and vertical forces. The condition reduces to mu >= 1/(2 tan theta).
Structured interviews that combine technical problem-solving with motivation and personal statement discussion.
Imperial interviews vary by department. Engineering and Computing tend to be technical with problem-solving elements. Medicine uses a Multiple Mini Interview (MMI) format with several short stations. Most interviews last 15-30 minutes and may include a presentation or group exercise.
Interview Invitation
Late Nov
Arrival to Interview
Early Dec
Technical Question
Mid Dec
Decision
Early Jan
Interview Invitation
Late Nov
Arrival to Interview
Early Dec
Technical Question
Mid Dec
Decision
Early Jan
Why does a helium balloon move forwards when a car it is inside accelerates, while the passengers are pushed back?
entryHint
Think about the pressure gradient the air develops under acceleration and buoyancy relative to the surrounding air. The balloon is less dense than air, so it behaves oppositely to a dense object.
A satellite in a low circular orbit experiences a tiny amount of atmospheric drag. Does it speed up or slow down? Justify your answer carefully.
midHint
Counter-intuitively it speeds up. Use the relationship between orbital radius and speed for a circular orbit, and note that losing energy shrinks the orbit while increasing v.
Explain physically, not just mathematically, why the kinetic energy of a moving object depends on the square of its speed rather than linearly on speed.
midHint
Consider work done by a constant force over the distance travelled, and how that distance itself grows with speed. Alternatively integrate F dot v over time from rest.
Two identical resistors can be connected in series or in parallel across the same battery. In which arrangement is more total power dissipated, and why does the battery notice the difference?
entryHint
Compare the equivalent resistance in each case and use P = V^2/R at fixed voltage. Lower equivalent resistance draws more current and dissipates more power.
The exhaust from a jet engine is hot. If we could make the exhaust come out cold instead, what would that tell us about the engine's efficiency, and why can't we make it perfectly cold?
hardHint
Frame this through the second law and the Carnot limit: rejected heat is unavoidable for a cyclic engine operating between two temperatures. A colder exhaust means less waste heat, but zero waste heat would need an infinite temperature ratio.
If you shrank yourself to the size of an ant but kept the same proportions and material, could you still jump over an obstacle your own height? Reason it out from scaling.
midHint
Compare how muscle force scales with cross-sectional area (length squared) against how weight scales with volume (length cubed). Jump height turns out to be roughly scale-independent, which is the surprising conclusion to defend.
Suppose the value of the gravitational constant G suddenly doubled everywhere. Walk me through what would happen to the Earth's orbit and to a person standing on the ground.
hardHint
Consider both the surface gravity g and the orbital dynamics; the current orbit is no longer circular for the new force, so discuss whether it becomes bound-but-elliptical. Keep track of what stays fixed (radius, speed) at the instant of the change.
How much would you weigh at the centre of the Earth? Assume uniform density and explain your reasoning before giving a number.
midHint
Use the shell theorem: only mass at smaller radius contributes, so the enclosed mass falls to zero at the centre. The gravitational field is therefore zero there.
Estimate the power output you would need to sustain to hover in still air like a helicopter, using your own mass. What physical bottleneck makes human-powered hovering essentially impossible?
hardHint
Model the momentum flux imparted to a column of air and relate thrust to the air mass accelerated downward per second. The required power scales unfavourably, far beyond sustained human output of a few hundred watts.
Your statement mentions a physics book or lecture series that shaped your thinking. Pick one idea from it and explain it to me as if I had never studied physics.
entryHint
Choose something you genuinely understand rather than the most impressive-sounding topic. Imperial values a clear, honest explanation and willingness to be probed on the details.
You describe a practical or project you carried out. What was the largest source of uncertainty in your results, and how would you redesign the experiment to reduce it?
midHint
Distinguish random from systematic error, and give a concrete, proportionate improvement. Showing you can critique your own work is stronger than claiming it went perfectly.
Why Physics at Imperial specifically, rather than Physics elsewhere or a related subject like Engineering or Mathematics? Be honest about the trade-offs.
entryHint
Anchor the answer in what Imperial's course actually offers and how it fits your interests. Avoid generic prestige claims; reference the balance of mathematics, computation and experiment that drew you.
You mention an area of modern physics you find exciting. What is one thing about it that you do not yet understand, and how might you go about learning it?
midHint
Naming a genuine gap and a credible route to close it signals intellectual honesty and independence, which is exactly the mindset a research-intensive department is looking for.
12+ weeks before chosen ESAT sitting
8-12 weeks before chosen ESAT sitting
4-6 weeks before chosen ESAT sitting
1-2 weeks before chosen ESAT sitting
after ESAT and before UCAS deadline
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Department-facing admissions presentation for applicants considering Physics at Imperial.
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Further Reading
by Richard P. Feynman, Robert B. Leighton and Matthew Sands
A broad conceptual bridge from school physics to university-style reasoning.
by Lewis Carroll Epstein
Useful for developing intuition, estimation and qualitative reasoning in mechanics, heat and waves.
by Brian Cox and Jeff Forshaw
Accessible enrichment for quantum ideas that can support personal-statement exploration.
by Brian Cox and Jeff Forshaw
A readable introduction to relativity and the link between physical intuition and mathematics.
by K. F. Riley, M. P. Hobson and S. J. Bence
Advanced reference for applicants who want to stretch beyond A-level mathematics; not required for admission.
by UAT-UK
Primary source for ESAT format, scoring, module selection and test-day rules.
by UAT-UK
Official specifications, guide and specimen/practice tests.
by Imperial College London Department of Physics
Department-level admissions information; editors should re-check manually because the page was not fetchable in this browsing pass.
by University of Cambridge and partners
Good source of non-calculator physics and maths practice at sixth-form-to-university transition level.
by Imperial College London
Primary place to check eligibility for contextual consideration.