Physics: Mechanics, Fluids and Heat
Must-know concepts
Units and measurement (SI base units, scalars versus vectors), kinematics (distance, displacement, speed, velocity, acceleration), Newton's three laws, momentum and impulse, work, power and energy, gravitation, pressure in fluids and Archimedes' principle, heat and temperature, simple machines, and basic electricity (Ohm's law, series and parallel circuits).
Traps to watch
- Mass versus weight: mass in kilograms is constant; weight in newtons depends on g.
- Distance versus displacement: displacement can be zero over a closed path even when distance is large.
- Newton's third law: action and reaction act on different bodies, so they never cancel.
- Floating: an object floats when its density is less than the fluid's, and the buoyant force equals the weight of displaced fluid.
- Series versus parallel: current is the same in series; voltage is the same in parallel.
- Heat versus temperature: a bathtub of warm water holds more heat than a cup of boiling water.
Rule of thumb
Draw a quick free-body diagram or circuit sketch. Label every force or component before writing an equation. Most errors in this paper come from a missing force or a misread unit, not from the formula itself.
Worked example
A 2 kg object accelerates at 3 m/s². Find the net force and the work done over 5 m. F = ma = 2 × 3 = 6 N. Work = F × d = 6 × 5 = 30 J. If the question had given weight instead of mass, you would divide by 9.8 first.