Physics: Mechanics, Electricity, Waves and Modern Physics
Physics on the ETEA engineering test samples the FSc (HSSC) syllabus: mechanics, electricity and magnetism, waves and optics, thermodynamics, and modern physics. Items are single-best-answer and reward clean application of a principle over long derivation, so identify which law a stem is testing before you compute.
Core rules to hold
- Newton's second law is a vector equation: F_net = ma, and weight W = mg acts downward while the normal force acts perpendicular to the surface.
- In projectile motion the horizontal velocity stays constant (no acceleration) while the vertical motion is free fall with a = −g.
- Ohm's law V = IR applies to ohmic conductors at constant temperature; series resistors add, parallel resistors satisfy 1/R = 1/R₁ + 1/R₂.
- For a converging lens or concave mirror, 1/f = 1/v + 1/u with your textbook's sign convention, and magnification m = v/u.
- Use work–energy when time is unknown and constant-acceleration kinematics when it is not.
Worked example
A ball is thrown straight up at 20 m/s. Taking g = 10 m/s², find the maximum height and the total time of flight. At the top v = 0, so v² = u² − 2gh gives 0 = 400 − 20h, hence h = 20 m. Rise time is t = u/g = 2 s; the fall takes the same time, so total flight is 4 s.
Traps that cost marks
- Switching between g = 9.8 and g = 10 mid-question; use the value the paper states.
- Treating mass and weight as interchangeable, so grams are plugged in where newtons are needed.
- Believing acceleration is zero at maximum height because velocity is zero there.
- Sign errors when displacement is upward but the chosen axis points downward.