MDCAT Physics Formula Traps 2026 — What the Options Are For

How MDCAT Physics distractors are built

Almost every numerical in this bank has four numbers that all come from the stem. One used the right formula. One dropped a ½ or a cosine. One used sin when the formula wanted cos (or the other way round). One added the given quantities as if they were the same kind of thing.

If you catch yourself thinking ‘that option looks familiar’, it should: it is the parallel-sum, the missing half, or the swapped exponent. Name the theft before you pick.

Mechanics traps (Units 1–4)

These steal the most marks early, and they come back inside projectiles, torque and rolling.

• $3\mathrm{N}$ and $4\mathrm{N}$ at right angles are $5\mathrm{N}$, not $7\mathrm{N}$.
• Out and back, average velocity is 0; average speed is not.
• From rest, $s=\frac{1}{2}a{t}^2$ — the ½ is not optional.
• Range uses sin 2 $\theta$, not sin $\theta$. Height uses only u sin $\theta$.
• Lift: $N=m(g+a)$ going up, not mg.
• Work is Fs cos $\theta$, a scalar. A static hold does no work.
• Centripetal force is the net toward the centre, not a third arrow. It does no work.

Fluids, waves, heat, fields (Units 5–8)

Continuity squares the radius. SHM does not carry amplitude. Coulomb is 1/r², potential is 1/r.

• Halve the pipe radius, speed ×4, not ×2.
• Faster fluid, lower pressure — never the other way in Bernoulli.
• Period of SHM does not carry amplitude. $T=2\pi \sqrt{m/k}$, not the upside-down version.
• Cp − $Cv=R$, and isochoric work is zero. Adiabatic is not isothermal.
• Midpoint of two pluses: $E=0$, V is not.
• Discharging at $t=RC$ is 0.37 $Q_0$, not empty.

Circuits to nuclei (Units 9–16)

Matching, Lenz, diodes, photons and half-lives each have one favourite lie.

• Power in the load peaks at $R=r$, not at $R=0.$
• Magnetic fields do no work. $r=mv/qB,not\propto B.$
• A static magnet in a coil is zero emf. Transformers do not rectify.
• ICE in a capacitor (current leads). Radio is not slower than gamma in vacuum.
• Half-wave does not double f. $V_{dc}$ is Vm/ $\pi$, not 2Vm/ $\pi$.
• Photons: $E=hf.$ Intensity is count. Threshold is a frequency gate.
• Balmer is visible, Lyman is not. $10.2\mathrm{eV}$ is 1→2, not ionization.
• $\lambda$ = 0.693/ $T_{1/2}$. Three half-lives leave 1/8, not 1/3. Heat does not hurry decay.

A 30-second check before you lock

1. What quantity did the stem actually ask — speed or velocity, E or V, power or energy?
2. Is there a ½, a cosine, or a square that the distractor dropped?
3. Is $g=10$ in this bank? Do not smuggle 9.8 into the arithmetic.
4. Lock. Then let the lab confirm, not suggest.