Physics
What the physics section tests
OAT physics covers mechanics, fluids, waves and sound, optics, electricity and magnetism, thermodynamics, and modern physics. Most items are one- or two-step applications of a formula, but conceptual questions about direction, sign, and conservation are common.
Core rules
- Kinematics: for constant acceleration, v=v0+at and Δx=v0t+½at². Choose a positive direction and keep it.
- Newton’s laws: net force causes acceleration; static friction adjusts up to μsN. An object in equilibrium has zero net force.
- Energy: conservation of mechanical energy applies when only conservative forces do work; friction removes mechanical energy as heat.
- Fluids: continuity A1v1=A2v2; Bernoulli relates pressure, height, and speed. Pressure increases with depth.
- Circuits: V=IR; resistors in series add; parallel branches share voltage.
- Waves/optics: v=fλ; for a converging lens, 1/f=1/do+1/di.
Worked example
A car starts from rest and accelerates at 2.0 m/s² for 5.0 s. How far does it travel? Use Δx=v0t+½at². v0=0, so Δx=½(2.0)(5.0)²=½(2.0)(25)=25 m. If the question instead gave final speed, you would first find v=at=10 m/s; average speed would be 5 m/s, giving the same 25 m.
Traps
- Mixing units (cm with m) or forgetting to square time.
- Treating static friction as always μsN rather than a maximum.
- Reversing the sign of g or of a vector component.
- Assuming a parallel circuit has the same current in each branch.
- Using degrees instead of radians in formulas that require radians.