Physics: Motion, Force, Energy and Circuits
What is tested
Physics questions usually cover measurement and SI units, motion, force and Newton's laws, work, energy and power, pressure and density, heat and temperature, light, electricity, magnetism, and simple machines. Numerical items are short and formula-based; conceptual items test definitions and distinctions.
Core rules
- Speed = distance ÷ time. Velocity is speed with direction. Acceleration = change in velocity ÷ time.
- Newton's second law: F = ma. Weight = mg, with g ≈ 9.8 m/s² near Earth's surface.
- Work = force × distance moved in the direction of the force. Power = work ÷ time.
- Density = mass ÷ volume. Pressure = force ÷ area. Liquid pressure = ρgh.
- Ohm's law: V = IR. Resistances in series add; in parallel, 1/R = 1/R₁ + 1/R₂ + …
- For reflection, angle of incidence = angle of reflection. Light entering a denser medium bends toward the normal.
Worked example
A 2 kg object accelerates at 3 m/s². The net force is F = ma = 2 × 3 = 6 N. If friction is 4 N, the applied force must be 6 + 4 = 10 N. The trap is reporting 6 N as the applied force and ignoring friction, or multiplying mass by g out of habit.
Traps
Prefix errors (kHz, mA, cm³), confusing mass with weight, treating scalars as vectors, and substituting diameter where radius is required. Always write the formula, substitute with units, then compute.