2.  Acceleration is the rate at which velocity changes over time  An object is accelerating if: 1. it is changing speed 2. it is changing direction 3. it is changing both speed and direction

3.  Positive Acceleration – an increase in velocity (speeding up)  Negative Acceleration or Deceleration– a decrease in velocity (slowing down)  Centripetal Acceleration – The acceleration that occurs in a circular motion

4. Let’s Practice! Justin Timberlake is running at a velocity of 4 ft/s South when a crazy fan starts chasing after him. Within 2 seconds he increases his speed to 8 ft/s to get away. What is his acceleration? Average acceleration = time it takes to change velocity final velocity – starting velocity

5. A = V f - V i t A = 8 ft/s - 4 ft/s 2 s A = 2 (ft/s)/s South or 2 ft/s 2 South 1. V f = 8 ft/s 2. V i = 4 ft/s 3. t = 2 s Average acceleration = final velocity – starting velocity time it takes to change velocity This means that every second JT’s velocity increases by 2 feet per second

6. More Practice: Calculate the bikers acceleration Av. Acceleration = 5m/s – 1m/s = 4s 1m/s2 south

7. More Practice: Calculate the bikers acceleration A plane passes over point A at a velocity of 240m/s north. Forty seconds later, it passes over point B a velocity of 260 m/s north. What is the plane’s average acceleration?

8. Recognizing Acceleration on a Graph The roller-coaster moves up the hill until it stops. Then you are off! This graph shows your acceleration for the next 10 seconds. Explain: During the first 8 seconds you have (+) acceleration. Then you begin climbing the next hill so for the next 2 seconds you experience( -) acceleration

9.  An object traveling in a circle is always changing its direction, therefore it is always changing its velocity, so it is accelerating  Examples: Windmill, Ferris Wheel, Roller Coaster Loops

10. 1. In 0.5 seconds, a missile goes from 0 to 300 m/s. What is the acceleration? 2. A meteoroid changed velocity from 1.0 km/s to 1.8 km/s in 0.03 seconds. What is the acceleration? 3. A race car driver is moving at 200 km/min when he slams on his brakes. He comes to a complete stop in 3 mins. What is his acceleration (or deceleration)? 4. A space ship releases a satellite into orbit. The satellite falls to earth at a speed of 1700 m/s in 25 seconds. What is the acceleration?