8 Common ESAT Distractor Traps & How to Beat Them

How ESAT Distractor Foils Are Crafted#

Incorrect options on the ESAT are not random. Each wrong option reflects a documented cognitive slip:

• Forget the minus sign in Lenz's law? That is Option B.
• Calculate radius instead of diameter? That is Option C.
• Forget the factor of $\frac{1}{2}$ in kinetic energy? That is Option D.

Recognizing these blueprints allows you to spot and prune traps before calculating.

Trap 1: Fence-Post & Boundary Errors#

• The Trap: Confusing intervals with endpoints ($n$ vs $n+1$). For example, 5 nodes on a standing wave contain 4 half-wavelengths ($2\lambda$), not $5\lambda$.
• The Fix: Sketch the boundary points. For intervals, count the spaces between posts, not the posts themselves.

Trap 2: Sign & Direction Flips#

• The Trap: Reversing direction vectors or negative work (e.g. work done by gravity vs against gravity, or Lenz's law $\mathcal{E} = -N\frac{d\Phi}{dt}$).
• The Fix: Always establish your coordinate convention (+ is up/right) before setting up the equation.

Trap 3: Factor of Two & Stoichiometry Omissions#

• The Trap: Missing or doubling a factor of 2 in formulas ($E_k = \frac{1}{2}mv^2$, spring energy $\frac{1}{2}kx^2$, circle area $\pi r^2 = \frac{\pi d^2}{4}$). In chemistry, forgetting that oxygen gas is diatomic $\text{O}_2$.
• The Fix: Double-check powers of 2 and stoichiometric coefficients before selecting your answer.

Trap 4: Intermediate Stop Foils#

• The Trap: Stopping calculation after finding an intermediate variable (e.g. finding acceleration $a = 2\text{ m s}^{-2}$ when the question asks for total distance $s$).
• The Fix: Re-read the final sentence of the question prompt before clicking your option.

Trap 5: Multi-Statement Linchpin Combinations#

• The Trap: Spending time evaluating all three statements (I, II, and III) independently.
• The Fix: Evaluate the easiest statement first. If Statement II is false, eliminate all options containing II. You rarely need to check all three.

Traps 6–8: Subsystem Isolation, Unit Prefixes & Table Pruning#

• Trap 6 (Subsystem Isolation): Applying $F = ma$ to the entire connected system when asked for internal tension between two bodies.
• Trap 7 (Unit Prefixes): Exponent slips when converting volumes: $1\text{ cm}^3 = 10^{-6}\text{ m}^3$ (not $10^{-2}$ or $10^{-3}$).
• Trap 8 (Table Pruning): Correctly matching Column 1, but flipping adjacent values in Column 2. Cross off eliminated rows on your scratchpad.

How Sub90's Mistake Bank Protects You#

When you practice on Sub90, every incorrect attempt is automatically tagged with its trap taxonomy and routed to your Mistake Bank. You clear items through spaced repetition drills, ensuring you do not repeat the same errors on test day.

Explore all 8 clinics in Common Exam Traps.