1. Motion
Chapter 2

2. Section 1
Describing Motion

3. Motion and Position
Motion – when an object changes its position relative to a reference point
Position of an object is determined relative to a reference point.

4. Motion Distance – how far an object has moved
SI unit for distance will be the meter (m)
Displacement – distance and direction of an object’s change of position from a starting point

5. Distance and Displacement
The length of displacement and distance will be the same if the motion is in a single direction.

6. Distance and Displacement
Distance would be the path that was travelled… while displacement is distance and position from the starting point

7. Speed
Speed is the distance an object travels per unit of time. Speed is a rate.
Rate – any change over time
Speed = distance (in meters)
time (in seconds)
Speed will be measured in rates of meters per second (m/s)

8. Units of speed
Sometimes it will be more convenient to measure speed in other units
Examples
Rocket going into space – km/s
car driving down the highway – km/h
geological plate movements – cm/year
baseball being thrown – m/s

9. Constant vs. Changing speed
Speed that does not change over time is a constant speed
Usually speed will not be constant. When the speed is not held at a constant rate this is called changing speed.

10. Average Speed Speed of motion when sped is changing.
This will use the total distance travelled divided by the total time of travel.
Average Speed = total distance
total travel time

11. Instantaneous Speed
The speed at any given point in time.

12. Graphing Motion
A distance-time graph displays motion of an object over time.
Plot distance on a vertical axis (y-axis)
Plot time on a horizontal axis (x-axis)
The slope of the line plotted on the distance-time graph is the speed.
Board example

13. Velocity Velocity - The speed and direction of an object’s motion
Ex. A race car has a constant speed and is going around an oval track. Even though the speed remains constant, the velocity changes b/c the direction of the car’s motion is changing constantly.

14. Section 2
Acceleration

15. What is acceleration? Acceleration is the rate of change of velocity.
When the velocity of an object changes, the object is accelerating.
Acceleration occurs when an object changes its speed, its direction, or both.

16. Types of Acceleration Positive acceleration – speed is increasing
2. Negative acceleration – speed is decreasing
3. Changing Direction
When an object changes speed or direction, it is accelerating.

18. Acceleration
Velocity
When the speed of the car is increasing the car has positive acceleration.
Acceleration
Velocity
When the speed of the car is decreasing the car has negative acceleration.

19. Calculating Acceleration
Acceleration = change in velocity time
A = Vf – Vi t
Change in velocity = final velocity – initial velocity
V = Vf - Vi

20. Calculating Acceleration
Unit for acceleration – meters per second squared
m/s2
There can be positive or negative acceleration.
Positive acceleration will have a final velocity that is more than the initial velocity.

21. Section 3
Motion and Forces

22. Motion and Forces
Force – a push or a pull that one body applies to another

23. Force A force can cause an object’s motion to change
When two or more forces combine at the same time, they create a net force
Balanced forces are equal in size and opposite in direction
Unbalanced forces are unequal in size and/or are not in the same direction

24. Force Changes Motion

25. Net Force

26. Newton’s First Law
An object at rest will stay at rest unless acted on by another force. And an object in motion will stay in motion unless acted on by another force.
Aka the Law of Inertia

27. Inertia Inertia – an object’s resistance to any change in motion
Objects with greater mass have greater inertia

28. Newton’s Law of Inertia in Action