Physics
Physics on the OAT is algebra-based and tests mechanics, fluids, waves, optics, electricity and magnetism, and thermodynamics. Success depends on choosing the right principle, keeping units consistent, and using signs correctly.
Core rules
- Newton’s second law: F_net = ma. Resolve forces into components on inclines and for tension problems.
- Conservation laws apply only under stated conditions: mechanical energy is conserved without nonconservative work; momentum is conserved when external net force is zero.
- Fluids: pressure increases with depth as P = P₀ + ρgh; buoyant force equals the weight of displaced fluid. Continuity and Bernoulli equations link speed, pressure, and area.
- Waves: v = fλ. For a converging lens or mirror, 1/f = 1/dₒ + 1/dᵢ, with magnification m = −dᵢ/dₒ using the standard sign convention.
- Circuits: V = IR; series resistances add; parallel branches share voltage. Power is P = IV.
Worked example
An object is 15 cm from a converging lens with focal length 10 cm. Use 1/f = 1/dₒ + 1/dᵢ: 1/10 = 1/15 + 1/dᵢ, so 1/dᵢ = 1/30 and dᵢ = 30 cm. The image is real and inverted; magnification = −30/15 = −2, so it is twice as large.
Traps
Do not mix centimeters and meters; do not ignore direction in vectors; do not apply conservation when friction or external forces act; do not drop the negative sign for inverted images; do not treat series and parallel resistors alike.