1. September 3, 2010 Average Speed, Velocity, Acceleration

2. Average Speed and Average Velocity  Average speed describes how fast a particle is moving. It is calculated by:  Average velocity describes how fast the displacement is changing with respect to time: always positive sign gives direction

3. Average Acceleration  Average acceleration describes how fast the velocity is changing with respect to time. The equation is: sign determines direction

4. Sample problem: A motorist drives north at 20 m/s for 20 km and then continues north at 30 m/s for another 20 km. What is his average velocity? 24 m/s

5. Sample problem: It takes the motorist one minute to change his speed from 20 m/s to 30 m/s. What is his average acceleration? 0.167 m/s 2

6. Average Velocity from a Graph t x A B xx tt

7. t x A B xx tt

8. Average Acceleration from a Graph t v A B xx tt

9. Sample problem: From the graph, determine the average velocity for the particle as it moves from point A to point B. 0 -2 1 2 00.10.20.30.40.5 -3 3 t(s) x(m) A B -1.0 m/s

10. Sample problem: From the graph, determine the average speed for the particle as it moves from point A to point B. 0 -2 1 2 00.10.20.30.40.5 -3 3 t(s) x(m) A B 1.0 m/s