1. Ch. 11: Motion 11.1: Distance and Displacement
11.2: Speed and Velocity
11.3: Acceleration

2. Choosing a Frame of Reference
To describe motion accurately and completely, a frame of reference is necessary.
A frame of reference is a system of objects that are not moving with respect to one another.
Choosing a meaningful frame of reference allows you to describe motion in a clear and relevant manner.

3. Measuring Distance
Distance is the length of a path between two points.
Start
End
Start
End

4. Measuring Distance
The SI (International System of Units) unit for distance is the meter.

5. Measuring Displacements
Displacement is the direction from the starting point and the length of a straight line from the starting point to the ending point.

6. Combining Displacements
Vector is a quantity that has magnitude and direction.
The magnitude can be size, length, or amount.

7. Displacement Along a Straight Line
The length of the arrow show the magnitude of the vector.
Vector addition is the combining of vector magnitudes and directions.

8. Displacement That Isn’t Along a Straight Path
The vector in red is called the resultant vector.

9. 11.2: Speed & Velocity
Speed is the ratio of the distance an object moves to the amount of time the object moves.

10. Speed Average Speed: is computed for the entire duration of a trip.
Instantaneous Speed: is measured at a particular instant.

11. Average Speed vs. Instantaneous Speed

12. To determine a speed, you need to know two things.
The distance traveled
The time taken
Speed is calculated by taking the distance traveled divided by the time taken.

13. Average Speed

14. SI Unit for Speed or Velocity
meter
second m s or

15. Three forms of the speed formula
Equation
Gives you…
If you know…
v = d/t
Speed
Time and distance
d = vt
Distance
Speed and time
t = d/v
Time
Distance and speed

17. What does “per” mean?
The word “per” means “for every” or “for each” or “divided by”.
If you want speed in meters per second, you have to divide meters by seconds.

18. Graphing Motion
The slope of a line on a distance-time graph is speed.

20. Velocity Is a description of both speed and direction of motion.
Velocity is a vector.

21. 11.3: Acceleration
A change in speed, change in direction, or change in both.
Acceleration is a vector.

22. Changes in Speed
Acceleration can be caused by positive (increasing) change in speed or by negative (decreasing) change in speed.

23. Free Fall
Objects falling near Earth’s surface accelerate downward at a rate of 9.8 m/s2.

24. Constant Acceleration
A steady change in velocity.

25. Instantaneous Acceleration
How fast a velocity is changing at a specific instant.

26. Calculating Acceleration
Calculate acceleration for straight-line motion be dividing the change in velocity by the total time.

27. Units for Acceleration
If speed is in m/sec and time in seconds, then the units for acceleration are m/sec/sec.
What this means is that the acceleration is the amount that the speed changes in each second.

29. SI Units for Acceleration
The units of square seconds do not have a physical meaning in the same way that square inches mean surface area.
meters
seconds2 or m s2

30. Graphs of Accelerated Motion

31. Graphs of Accelerated Motion

32. A distance-time graph of accelerated motion is a curve.