1. Acceleration & Velocity Time Graphs
Chapter 2.2

2. acceleration Rate at which velocity is changing
acceleration= change of velocity
time
Acceleration = change of speed
(along a straight line) time

3. Acceleration occurs when there is either a change in speed, change in direction or both (whenever there is a change in velocity).

4. In physics, acceleration applies to both increases and decreases in speed
Decrease in speed= negative acceleration

5. Practice Problem
Suppose a car moving in a straight line steadily increases its speed each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then from 45 to 50 km/h. What is its acceleration?
Speed increases 5 km/h each 1 s interval, therefore acceleration= 5 km/h*s
(read 5 km per hour second)

6. Practice Problem 2
In 5 seconds a car moving in a straight line increases its speed from 50 km/h to 65 km/h, while a truck goes from rest to 15 km/h in a straight line in that same amount of time. Which undergoes the greater acceleration? What is the acceleration of each vehicle?
Acceleration for both vehicles is 15 km/h*s (the undergo the same acceleration even though their speeds are quite different)

7. Speed vs. Time Graphs X axis: always time Y axis: always speed
Slope of line = speed/time
Slope tells you what happens to acceleration of the object
Area under line tells you the distance the object traveled.

8. What is happening in this graph?
Objected started at rest
Speed is increasing
Object is accelerating

9. What is happening in this graph?
Object is slowing down
Object is negatively accelerating (decelerating)

10. What is happening in this graph?
Both objects are moving
Both objects are increasing speed but at different rates
Dashed line increases speed faster so it has the greater acceleration

11. What is happening in this graph?