uniform circular motion

Meaning: An object moves around a circle at constant speed. Its velocity is tangent to the path and keeps changing direction, so it accelerates even though its speed is constant. The acceleration points toward the center, perpendicular to velocity, so it changes direction only. This requires a net inward force, supplied by real forces such as tension, gravity, friction, or the normal force. If that force vanishes, the object leaves along the tangent.

Equation: ac = v²/r = ω²r and Fnet = mv²/r, where ac is centripetal acceleration (m/s²), v is speed (m/s), r is radius (m), ω is angular speed (rad/s), m is mass (kg), and Fnet is the inward net force (N). Also v = 2πr/T, with T the period (s).

On the MCAT: Typical setups are a car on a flat curve (friction provides the force), a mass on a string, a satellite in orbit, a centrifuge, or a charged particle in a magnetic field (qvB = mv²/r). Doubling v quadruples the required force; halving r doubles it. The centripetal force does no work because it is perpendicular to the displacement.

Common confusion: Centrifugal force is not a real force in an inertial frame; the apparent outward push is inertia, the tendency to go straight. Also, constant speed does not mean zero acceleration, because acceleration is a change in the velocity vector, direction included.