Physics: Forces, Motion, Energy, Electricity, Waves, and Light
Physics on this exam tests how you connect forces to motion, track energy transfers, reason about circuits and magnets, and apply wave and light relationships. Expect numerical items plus explanation items about cause and effect.
Forces and motion
Newton's second law is the central tool: net force = mass × acceleration (F_net = ma). Draw a free-body diagram before calculating. Weight is mg, not mass. Friction opposes relative motion and reduces net force. For constant velocity, net force is zero.
Energy
Energy is conserved but transforms. Kinetic energy = ½mv²; gravitational potential near Earth = mgh. Work = force × distance in the force direction. Power = energy transferred ÷ time.
Electricity and magnetism
Ohm's law: V = IR. In series, current is the same and voltages add; in parallel, voltage is the same and currents add. Magnetic fields surround currents and magnets; changing magnetic fields can induce voltage.
Waves and light
Wave speed v = fλ. Sound needs a medium; light can travel through vacuum. Reflection angle equals incidence angle; refraction bends light when speed changes between media.
Worked example
A 2.0 kg cart is pushed with 10 N while friction is 4 N. Net force = 10 − 4 = 6 N. Acceleration a = F_net/m = 6/2.0 = 3 m/s². From rest, after 2.0 s, v = at = 3 × 2.0 = 6 m/s. The reasoning depends on using net force, not the 10 N push alone.
Traps
Do not use applied force as net force when friction acts. Do not confuse mass and weight. In circuits, do not add currents in series as if they split. For waves, f and λ change inversely only if speed is fixed.