1. Average vs.Instantaneous Velocity

2. Uniform Constant Motion
What would the graph of position-time for this motion look like?

3. Uniform Constant Motion
The object moves 4.0 m in the time interval between t = 0 s and t = 4.0 s. Likewise, the object moves an additional 4.0 m in the time interval between t = 4.0 s and t = 8.0 s.
Because the average velocity does not change, the object is moving with a constant velocity of +1.0 m/s, and its motion is represented by a straight line on the position-time graph.

4. Average Speed & Instantaneous Velocity
The average speed depends ONLY on the distance traveled and the time required.
The instantaneous velocity is the magn-itude and direction of the speed at a par-ticular instant. (v at point C) A B
d = 20 m
Time t = 5 s C

5. - - The Signs of Velocity +
Velocity is positive (+) or negative (-) based on direction of motion. + -
First choose + direction; then v is positive if motion is with that direction, and negative if it is against that direction. + - +

6. Average & Instantaneous velocity
Average Velocity:
Instantaneous Velocity: Dx Dt x2 x1 t2 t1 Dx Dt
Time
slope
Displacement, x

7. EXAMPLE of the Average Speed
Q: What is the average speed of the car during the 5 seconds? A B
d = 20 m
Time t = 5 s C

8. EXAMPLE of a Moving Car

9. What is the average velocity of the car
during the first 10 seconds?
2. What is the
instantaneous velocity
of the car at point A?
3. What is the average velocity of the car
for the entire trip?