1. Acceleration
Measuring motion
By Vinesh Vora
Andrew Jaisingh

2. Acceleration Acceleration = speeding up
Acceleration – the rate at which velocity changes
Can be an:
Increase in speed
Decrease in speed
Change in direction

3. Types of acceleration Increasing speed Decreasing speed
Example: Car speeds up at green light
Decreasing speed
Example: Car slows down at stop light
Changing Direction
Example: Car takes turn (can be at constant speed)
screeeeech

4. Question
How can a car be accelerating if its speed is a constant 65 km/h?
If it is changing directions it is accelerating

5. Calculating Acceleration
If an object is moving in a straight line
Units of acceleration:
m/s2

6. Calculating Acceleration
0 s
1 s
2 s
3 s
4 s
0 m/s
4 m/s
8 m/s
12 m/s
16 m/s

7. Question
A skydiver accelerates from 20 m/s to 40 m/s in 2 seconds. What is the skydiver’s average acceleration?

8. Graphing Acceleration
Can use 2 kinds of graphs
Speed vs. time
Distance vs. time

9. Graphing Acceleration: Speed vs. Time Graphs
Speed is increasing with time = accelerating
Line is straight = acceleration is constant

10. Graphing Acceleration: Speed vs. Time Graphs
Rise = 4 m/s
Run = 2 s
In Speed vs. Time graphs:
Acceleration = Rise/Run
= 4 m/s ÷ 2 s = 2 m/s2

11. Graphing Acceleration: Distance vs. Time Graphs
On Distance vs. Time graphs a curved line means the object is accelerating.
Curved line also means your speed is increasing. Remember slope = speed.

12. Area under a graph
The area under a velocity-time graph shows the distance an object has traveled.
In order to find the distance (m), multiply the velocity (m/s) by the time (s).
Area=(base)(height)
=(time)(velocity)
=distance
When the area under the velocity-time graph is a right triangle, the area is found using the equation.
Area=1/2base X height

13. Question:
What is the total distance traveled by the bus during the first 10 seconds?

14. Answer:
First, calculate the first 5 seconds, which is a right-triangle.
Area=1/2base X height
=1/2(5m)(10m/s)
=25m
Next, calculate the last 5 seconds, which is a rectangle.
Area=(base)(height)
=(time)(velocity)
=(5s)(10m/s)
=50m
Last, add the two totals to get the entire area under the graph, which is your total distance.
25m+50m=75m
Answer=75m

15. Question Run = 3 s Rise = -6 m/s
Above is a graph showing the speed of a car over time.
1) How is the speed of the car changing (speeding up,
Slowing down, or staying the same)?
2) What is this car’s acceleration?
The car is slowing down
Acceleration = rise/run = -6m/s ÷3s = -2 m/s2

16. curved line = accelerating, flat line = constant speed
Question:
The black and red lines represent a objects that are accelerating. Black is going a greater distance each second, so it must be speeding up. Red is going less each second, so must be slowing down
Remember: in distance vs. time graphs:
curved line = accelerating, flat line = constant speed
Which line represents an object that is accelerating?

17. Question: Hard one
Above is a graph showing the speed of a car over time.
1)What would a distance vs. time graph for this
look like?

18. Slopes of graphs reveal how objects move
Because the plane is moving at a
constant velocity, its acceleration
is zero.
It is called non-uniform motion because the object’s speed or direction
is changing.

29. Form to use when accelerating object has an initial velocity
Form to use when accelerating object starts from rest

30. Video