What is Acceleration Acceleration is a Vector Rate

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 / time 2 – e. g. , m/s 2, 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 ,

Constant vf = vi + a Δ t Δd = vav Δ t vav = (vf + vi)/2 Δd = vit + 0. 5 at 2 Δt = time d = displacement vi = initial velocity vav = average velocity 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 1. With an average acceleration of -1. 2 m/s 2, how long will it take a cyclist to bring a bicycle with an initial speed of 6. 5 m/s to a complete stop? n 2. A: 5. 4 s Suppose a treadmill has an average acceleration of 4. 7 × 10. 3 m/s 2. 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? n 1. 4 m/s and 3. 1 m/s