Acceleration = Change in velocity / change in time What is Acceleration?? Acceleration is a Vector!! Rate of change in velocity in a given time interval Describes how rapidly the velocity of an object is changing Acceleration = Change in velocity / change in time a (average) = Dv / Dt Units: length / time2 – e.g., m/s2, km/h/s

Average acceleration

Average Acceleration Other Equations: Rearranging, Dv = a ave Dt , OR, v(final) = v(initial) + a (avg) Dt

Think About It! If the acceleration of an object is zero, does that mean that the velocity is zero? Explain. If the velocity of an object is zero, does that mean that the acceleration must be zero?? Explain.

Just like Velocity Acceleration is a vector quantity Has both a magnitude (speed) AND direction Can be positive or negative JUST DIRECTIONAL!!!

Acceleration is the slope of a velocity vs. time curve. Since slope = rise/run, Just as ,

vf = vi + a Δ t Δd = vav Δ t vav = (vf + vi)/2 Constant Δ t = time d = displacement Δd = vav Δ t vi = initial velocity vav = (vf + vi)/2 vav = average velocity Δd = vit + 0.5at2 a = acceleration vf = final velocity

Kinematic Equations for Uniform Acceleration Variables missing acceleration displacement final velocity time Note: do left out for convenience

Practice problems With an average acceleration of -1.2 m/s2, how long will it take a cyclist to bring a bicycle with an initial speed of 6.5 m/s to a complete stop? A: 5.4 s Suppose a treadmill has an average acceleration of 4.7 × 10.3 m/s2. a. How much does its speed change after 5.0 min? b. If the treadmill’s initial speed is 1.7 m/s, what will its final speed be? 1.4 m/s and 3.1 m/s