Acceleration is the change in velocity in relation to time. If you were to observe acceleration in one dimension, acceleration is the rate at which something speeds up or slows down. Since velocity is a vector, acceleration is the rate of change of both the magnitude and direction of velocity. Acceleration is measured in (m/s2). Acceleration is the change in velocity (Δv) divided by the change in time (Δt) . Instantaneous acceleration is the acceleration at a specific point in time as Δt goes toward zero. The Velocity vs. Time graph below shows the direct relation of acceleration in a real situation.