—change in velocity divided by the time for the change to occur; it can include an object’s speeding up, slowing down, and/or changing direction. B. Acceleration can be if you know how an object’s velocity has changed during a given time period. 1. The formula for calculating is: acceleration = final speed – initial speed/time or a = (sf – si )/t. a. The unit of acceleration is distance divided by time squared; in SI units, acceleration is given as (m/s 2 ). b. Acceleration is when an object speeds up and when an object slows down. 2. Accelerated motion can be with speed on the vertical axis and time on the horizontal axis. a. An object that is speeding up will have a line on a speed-time graph that slopes . b. An object that is slowing down will have a line on a speed-time graph that slopes . c. A horizontal line would indicate acceleration of , or constant speed.