Quick Reference
Method first
Before writing a formula, identify what is known, what is asked and which physical principle connects them.
Units are evidence
A unit mismatch is often a clue that the wrong relationship was selected or a conversion was skipped.
Vectors are not optional
Magnitudes alone can hide direction, sign and component relationships.
Estimate before calculate
A rough scale check can expose a calculator error before it becomes a final answer.
1. Mechanics & Motion
| Relationship | Use it when… | Common trap |
|---|---|---|
| v = Δx / Δt | Average velocity from displacement and time. | Using total distance when the question asks displacement. |
| a = Δv / Δt | Average acceleration. | Forgetting velocity is directional. |
| v = u + at | Constant acceleration. | Applying it when acceleration is not constant. |
| s = ut + ½at² | Constant acceleration and known time. | Mixing displacement and distance. |
| v² = u² + 2as | Constant acceleration when time is inconvenient. | Using it with inconsistent sign conventions. |
| F = ma | Net force model. | Using a single force instead of the net force. |
| p = mv | Linear momentum. | Dropping direction in collision problems. |
2. Work, Energy & Power
Use conservation of energy when the question compares an initial state with a final state and the energy transfers can be accounted for cleanly. Use the work–energy theorem when the net work changes kinetic energy. Keep track of whether a force does positive, negative or zero work.
3. Circular Motion & Gravitation
Centripetal force is not a new species of force; it is the name for the net inward force required for circular motion. Depending on the situation, tension, friction, gravity or a normal force can supply that inward net component.
4. Fluid Dynamics
| Idea | Relationship | Interpretation |
|---|---|---|
| Pressure | P = F/A | Force distributed over area. |
| Hydrostatic pressure | ΔP = ρgΔh | Pressure change with depth in a fluid of uniform density. |
| Continuity | A₁v₁ = A₂v₂ | For steady incompressible flow, smaller area means greater speed. |
| Bernoulli | P + ½ρv² + ρgh = constant | Energy balance along a streamline under idealized conditions. |
5. Oscillations, Waves & Sound
Separate the speed of a wave from the oscillation frequency of its source. In a given medium, changing frequency can change wavelength while the wave speed remains constrained by the medium’s properties. This distinction is a frequent source of conceptual distractors.
6. Electricity & Circuits
For series resistors, current is the same through each resistor and the resistances add. For parallel resistors, the potential difference across branches is the same while conductances add. Always identify the circuit structure before inserting numbers.
7. Electrostatics & Fields
Watch vector direction. Electric field is a vector; electric potential is a scalar. The magnitude of a quantity may look identical in two options while the direction makes one physically impossible.
8. Thermal, Atomic & Nuclear Reminders
Use the correct physical meaning: specific heat capacity relates energy to temperature change; latent heat relates energy to phase change; photon energy is proportional to frequency. For atomic and nuclear topics, keep unit prefixes under control because energy values often span many powers of ten.
Frequently Asked Questions
PM&DC — Uniform Curriculum MDCAT-2025 (official PDF) · PM&DC — Public Notice regarding MDCAT-2026 · NIST — Guide to the SI, Chapter 4 · OpenStax — College Physics 2e: Physical Quantities, Units, Accuracy & Significant Figures · OpenStax — College Physics: Accuracy, Precision, and Significant Figures
Scope: scientific explanations are written for student use and simplified where appropriate. Exact exam wording, syllabus scope and current administrative rules should be checked against PM&DC documents.