Traps
How MHT-CET Physics loses you marks even when you know the physics
Two things make this exam's trap list unlike NDA's or JEE's, and neither is physics. The penalty for a wrong answer is 0, so every reflex built on an exam that deducts for a wrong answer is harmful here — and Physics shares a 90-minute paper with Chemistry, so several shapes below are TIME traps. At about 1.1 minutes a Physics question, that is where marks are lost.
- trap shapes
- 13
- strands affected
- 3
- playbooks hit by the widest trap
- 6
- paper-wide, not chapter-specific
- 2
How to use this page
Read it once cover-to-cover, then re-read the section matching your next practice block — a trap is far easier to spot when you have just been primed on its mechanism. One thing to know before you start: a trap is filed under the strand whose MARKS it costs you, not the strand the question sits in. Computing both sides of a ratio question is a cornerstone trap even when the question sits in a long-tail chapter, because what it takes from you is cornerstone time.
Cornerstone traps — where the marks actually go
These cost you cornerstone marks. Three of them are paper-wide — the blank bubble, the drifting clock and the ratio computed in full — and are filed here because the minutes they burn are the minutes the heaviest chapters needed.
Leaving a question blank — the most expensive habit on this paper
Paper-wide — not tied to any one chapter
The mechanic
MHT-CET has NO negative marking. A blank and a wrong answer are both worth zero, so the reflex carried in from other exams — leave it if unsure — turns a free attempt into a certain zero. On a 50-question Physics half, five blanks are five marks you chose not to be paid for.
The fix
Mark every uncertain question as you pass it, and keep the last three minutes of Paper II for filling every blank — eliminate what you can, then choose. An unfilled bubble is the only error on this paper that costs a mark with certainty.
No time split between Physics and Chemistry — the clock drifts to the harder subject
Paper-wide — not tied to any one chapter
The mechanic
Paper II is 100 questions in 90 minutes, Physics and Chemistry together, and it does not divide the time for you. Physics is 18% HARD and Chemistry about 3%, so the paper pulls minutes towards Physics until Chemistry questions you could have answered in thirty seconds are guessed at the end. The marks are equal: a Chemistry question is worth exactly what a Physics one is.
The fix
Decide the split before the paper — a starting budget of about 35 minutes for Chemistry and 55 for Physics — and a clock time to switch. Test it in two timed mocks and adjust by your own numbers. See Strategy.
Computing both values in a ratio question — 279 of them, in 22 chapters
Affects: Kinetic Theory of Gases, Thermal Properties of Matter, Structure of Atoms and Nuclei, Gravitation, Oscillations, Superposition of Waves
The mechanic
The word 'ratio' is in 279 question stems across 22 of the 24 chapters. Most ask how one quantity compares in two situations — two gases, two orbits, two temperatures, two strings. Computing each value in full doubles the arithmetic and doubles the chances of a slip, all to cancel most of it at the end.
The fix
Write the formula as a proportion first, keep only what changes, and cancel the rest: v_rms ∝ √(T/M), r ∝ n²/Z, P ∝ T⁴, T ∝ √(l/g), v ∝ √(T/μ). A ratio question answered this way takes a line and rarely needs a constant.
Changing a capacitor without asking what stayed constant
Affects: Electrostatics
The mechanic
The capacitor pages are 67 questions of Electrostatics, and nearly every change — a slab inserted, plates pulled apart — moves charge, voltage and energy in opposite directions depending on whether the battery is still connected. Both outcomes are printed.
The fix
Before any formula, write 'V fixed' (battery on) or 'Q fixed' (battery off). Then use U = ½CV² for the first and Q²/2C for the second.
Counting one surface on a soap bubble
Affects: Mechanical Properties of Fluids
The mechanic
Surface tension is two thirds of the Fluids chapter. A liquid drop has one surface; a soap bubble has two. So a bubble's excess pressure is 4T/r against a drop's 2T/r, and the work to blow a bubble is double the work to form a drop of the same size. The one-surface answer is always an option.
The fix
Before writing ΔP or W, ask: drop, air bubble in a liquid (one surface), or soap bubble in air (two)?
Adding intensities where amplitudes add
Affects: Wave Optics, Superposition of Waves
The mechanic
Waves superpose by amplitude, and intensity is amplitude squared. Two sources of intensity I and 4I give a maximum of 9I and a minimum of I, not 5I and 3I. Wave Optics spends 29 questions on interference intensity.
The fix
Take square roots, add or subtract, square again: I_max = (√I₁ + √I₂)², I_min = (√I₁ − √I₂)².
Using the perpendicular-axis theorem on a solid body
Affects: Rotational Dynamics
The mechanic
Parallel and Perpendicular Axis Theorems is 25 questions at 48% HARD — nearly half the chapter's HARD. The perpendicular-axis theorem holds only for flat bodies; applied to a sphere or a cylinder it gives a clean, wrong number.
The fix
Perpendicular axis: flat bodies only. Parallel axis: any body, but only from an axis through the centre of mass.
Quick-win traps — cheap marks lost to procedure, not difficulty
These sit in the cheapest chapters on the paper, and every one of them is a procedure error rather than a difficulty error. The physics is not what loses these marks.
Answering a figure question from what the figure usually shows
Affects: Semiconductor Devices, Magnetic Fields Due to Electric Current, Current Electricity
The mechanic
221 Physics questions across 19 chapters carry a figure, and they run 25% HARD against 18% for the bank. A gate circuit looks like a familiar gate and is another; a bridge looks balanced and is not; two wires look like their fields add and they cancel. The trap is recognising the picture instead of reading it.
The fix
Read every figure in full: trace each gate's truth table, check each bridge ratio, mark each field's direction. It costs twenty seconds and it is where the cheap chapters lose their marks.
Using Celsius where the law needs kelvin
Affects: Kinetic Theory of Gases, Thermal Properties of Matter, Thermodynamics
The mechanic
v_rms ∝ √T, P ∝ T⁴ and the Carnot efficiency 1 − T₂/T₁ all need absolute temperature. 27 °C to 927 °C is 300 K to 1200 K — a factor of 4 — and a Celsius ratio gives a number that is also printed.
The fix
Convert every temperature to kelvin before it enters a ratio or an efficiency. Differences (ΔT) can stay in Celsius; ratios cannot.
Adding the voltages across R, L and C as numbers
Affects: AC Circuits
The mechanic
In a series LCR circuit the voltages are out of phase, so they combine as V = √(V_R² + (V_L − V_C)²). Added as numbers they exceed the source voltage — a sign that something is wrong, and an option on the paper.
The fix
Draw the impedance triangle. The same triangle gives Z, the phase angle and the power factor.
Long-tail traps — the expensive chapters
These cost long-tail marks: a graph read the wrong way, a sign dropped in a lens formula, and prep hours still going to two chapters the 2025 papers halved.
Letting brighter light raise the stopping potential
Affects: Dual Nature of Radiation and Matter
The mechanic
The photoelectric page is 56 questions at 36% HARD, and its graph questions test one split: frequency sets the electrons' energy (and so V₀); intensity sets how many there are (and so the current). An option always lets intensity move V₀.
The fix
Ask which of the two changed. Intensity: current moves, V₀ stays. Frequency: V₀ moves, saturation current stays.
Dropping a sign in the lens or mirror formula
Affects: Ray Optics
The mechanic
In the Cartesian convention the object distance is negative and a concave lens has a negative focal length. One lost sign turns a real image into a virtual one, and both are options. Lenses and refraction are 50 of Ray Optics' 78 questions.
The fix
Write each value with its sign before substituting, and check the image type against the lens: a concave lens never forms a real image of a real object.
Giving Gravitation and Ray Optics the hours they earned in 2023-24
Affects: Gravitation, Ray Optics
The mechanic
Both chapters ran above two questions a paper through 2023-24 and both fell to about one in 2025. A student prepping from 2023-24 papers still gives them two questions' worth of hours — hours that the rising chapters (Rotational Dynamics, Motion in a Plane) needed.
The fix
Plan hours on the recent rate, not on the papers you happen to practise. Keep Gravitation's variation-of-g page (33 questions at 3% HARD) and trim the rest. See Trends.
The two habits that cover most of this page
Most of the 13 shapes above reduce to one of two disciplines, and neither of them is extra physics.
Before you start writing
Read, then compute
Is this a ratio question — write the proportion, not the values? What is held constant — Q or V, pressure or volume? Is the figure what it looks like — trace the gates, check the bridge, mark each field’s direction? Fifteen seconds of reading is cheaper than two minutes down the wrong route, and on about 1.1 minutes a question there is no cheap way back.
Before you hand the paper in
Nothing goes back unanswered
Mark every uncertain question as you pass it, and keep the last three minutes of Paper II free to fill whatever is still empty. A blank and a wrong answer score the same on this exam, so an unfilled bubble is the only error here that costs you marks with certainty rather than probability.