Physics: Mechanics, Energy, and Waves
Core concepts to master
Kinematics describes motion with displacement, velocity, and acceleration. Know the equations for constant acceleration, including v = v0 + at and d = v0 t + half a t squared. Newton's three laws connect force and motion, and free-body diagrams clarify net force. Work, energy, and power are central: work equals force times displacement, kinetic energy is half m v squared, and gravitational potential energy is m g h. Conservation of energy and momentum solves collision problems. Waves require wavelength, frequency, and speed, related by v = f times lambda. Electricity covers Ohm's law, series and parallel circuits, and power.
Traps to watch
Distinguish speed from velocity and distance from displacement; direction matters. Do not confuse mass with weight. In projectile problems, horizontal and vertical motions are independent, and vertical acceleration is gravity. Remember that in parallel circuits voltage is constant while current splits, and in series the reverse holds. Check whether a question asks for average or instantaneous values. Keep units consistent, converting kilometers to meters and minutes to seconds.
Worked example
A car accelerates from rest at 2 m/s squared for 5 s. Find its final velocity and distance. Using v = v0 + at, with v0 equal to zero, v equals 2 times 5, which is 10 m/s. Distance equals v0 t plus half a t squared, giving 0 plus half times 2 times 25, which is 25 m. Rule of thumb: list knowns, choose the equation containing the unknown, and verify units.