Acceleration Acceleration is the rate of change of velocity with respect to time. a = Δv = vf – vi Δt tf – ti The units for acceleration are m/s2

Acceleration An object is accelerating if it’s speed, direction, or both change. Acceleration can be: Speeding up Slowing down Changing direction If an acceleration is positive, the object is speeding up. If an acceleration is negative, the object is slowing down.

Acceleration Ex: Find the acceleration of an amusement park ride that falls from rest to a speed of 28 m/s in 3.0 s. G: vi = 0 m/s vf = 28 m/s Δt = 3.0 s U: a E: a = vf – vi Δt S: a = 28 m/s – 0 m/s 3.0 s S: a = 9.3 m/s2

Acceleration Ex: A shuttle bus slows down with an average acceleration of -1.8 m/s2. How long does it take the bus to slow from 9.0 m/s to a complete stop? G: a = -1.8 m/s2 vi = 9.0 m/s vf = 0 m/s U: Δt E: a = vf – vi  Δt = vf – vi Δt a S: Δt = 0 m/s – 9.0 m/s -1.8 m/s2 S: Δt = 5.0 s

Acceleration Graphs Velocity is on the y-axis, time is on the x-axis. The slope and shape of the graph describe the object’s motion.