1. Motion, Speed & Acceleration Review

2. Describe Motion

3. Motion

4. Reference Point

5. Frame of Reference

6. Frame of Reference Example

7. Describe Speed

8. Speed

9. Describe Speed A way to describe motion
Average speed - Rate of motion calculated by dividing the distance traveled by the amount of time it takes to travel that distance
Constant speed - Speed that does not change
Instantaneous speed - Speed of an object at any given time

10. What is the formula used to calculate speed?

11. What is the formula for calculating speed?
Speed is calculated by dividing distance by time –

12. Calculate This Speed
A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast was the football player running?

13. Remember to include the UNITS!!
Calculate this Speed:
A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast was the football player running?
Speed = Distance ÷ Time
Speed = 100 m ÷ 20 s
Speed = 5m/s
Remember to include the UNITS!!

15. Describe Velocity

17. Distinguish Between Speed and Velocity
Speed describes distance and time
Velocity describes distance, time, and direction

18. Describe Acceleration
A change in velocity – which may be:
A change in speed
Starting
Stopping
Speeding up
Slowing down
A change in direction
Acceleration is caused by unbalanced forces
More

19. Describe Acceleration

20. Describe Acceleration
Deceleration is called negative acceleration - it means an object is slowing down
When acceleration is calculated, it may be a negative number

21. Calculating Acceleration
To determine the acceleration of an object moving in a straight line, you must calculate the change in speed per unit of time.

22. Calculating Acceleration
As a roller-coaster car starts down a slope, its speed is 4 m/s. But 3 seconds later, at the bottom, its speed is 22 m/s. What is its average acceleration?
Read and Understand
What information have you been given?
Initial speed = 4 m/s
Final Speed = 22 m/s
Time = 3 s

23. Calculating Acceleration
As a roller-coaster car starts down a slope, its speed is 4 m/s. But 3 seconds later, at the bottom, its speed is 22 m/s. What is its average acceleration?
Plan and Solve
What quantity are you trying to calculate?
The average acceleration of the roller-coaster car = __
What formula contains the given quantities and the unknown quantity?
Acceleration = (Final speed – Initial speed)/Time
Perform the calculation.
Acceleration = (22 m/s – 4 m/s)/3 s = 18 m/s/3 s
Acceleration = 6 m/s2
The roller-coaster car’s average acceleration is 6 m/s2.

24. Calculating Acceleration
As a roller-coaster car starts down a slope, its speed is 4 m/s. But 3 seconds later, at the bottom, its speed is 22 m/s. What is its average acceleration?
Look Back and Check
Does your answer make sense?
The answer is reasonable. If the car’s speed increases by 6 m/s each second, its speed will be 10 m/s after 1 second, 16 m/s after 2 seconds, and 22 m/s after 3 seconds.

25. Calculating Acceleration
Practice Problem
A falling raindrop accelerates from 10 m/s to 30 m/s in 2 seconds. What is the raindrop’s average acceleration?
(30 m/s – 10 m/s) ÷ 2 seconds = 10 m/s2

26. Calculating Acceleration
Practice Problem
A certain car can accelerate from rest to 2.7 m/s in 9 seconds. Find the car’s average acceleration.
(27 m/s – 0 m/s) ÷ 9 s = 27 m/s ÷ 9 s = 3 m/s2

27. Distinguish Between Position/Distance vs
Distinguish Between Position/Distance vs. Time Graphs and Speed/ Velocity vs.Time Graphs

28. Graphing Acceleration
You can use both a speed-versus-time graph and a distance-versus-time graph to analyze the motion of an accelerating object.

29. Position/Distance vs. Time Graphs (slope = speed)

30. Interpret The Graph Below:

31. Interpret The Graph Below:
The graph shows an object which is not moving (at rest).
The distance stays the same as time goes by because it is not moving.

32. Interpret The Graph Below:

33. Interpret The Graph Below:
The graph shows that the objects distance increases as time passes. The object is moving and so it has velocity.
The straight line shows it is a constant (not changing).

34. Interpret The Graph Below:

35. Interpret The Graph Below:
Just like the previous graph, this graph shows an object moving with constant velocity

36. Interpret The Graph Below:

37. Interpret The Graph Below:
The curve in the graph shows that the objects velocity is changing as time passes.
This is acceleration.

38. Interpret The Graph Below:

39. Interpret The Graph Below:
In the first part of the graph the object is moving with constant velocity.
In the second part of the graph the object is at rest (not moving).
In the third part the object is again moving with constant velocity.

40. Velocity vs.Time Graphs (slope = acceleration)

41. Interpret The Graph Below:

42. Interpret The Graph Below:
The graph shows that the objects velocity does not change as time passes.
It shows constant velocity.

43. Interpret The Graph Below:

44. Interpret The Graph Below:
The graph shows that the objects velocity is increasing as time passes – it is accelerating.
The straight line shows that it is constant acceleration.