1. Motion, Forces and Energy
Chapter 1

2. Chapter 1: Motion Section 1: Describing and Measuring Motion
When is an object in motion?
How do you know an object’s speed and velocity?
How can you graph motion?

3. Section 1: Describing and Measuring Motion
Observing Motion:
Motion: distance from another object changes
Reference Point
An object that appears to be in place or an object used for comparison to detect motion
Object in motion if it changes position relative (compared to ) the reference point
Relative Motion
Motion dependent on reference point
Example: sky divers

4. Observing Motion Common Reference Point
Nonmoving objects such as buildings, trees, and mountains
Moving objects could also serve as reference point; bird flying by hot air balloon
Earth is a moving reference point; moving around the Sun

5. Section 1: Describing and Measuring Motion
Measuring Distance
International System (SI) : system of measurement used around the world
Meter: SI unit of length

6. Speed Depends on Distance and Time
Speed—the rate at which an object moves
Depends on distance travelled and time taken to travel distance
SI unit—meters per second m/s
The Speed Equation
Speed = Distance/Time
Example: 30m/5s = 6m/s

7. Section 1: Calculating Speed
Average Speed
Average Speed = Total Distance/Total Time
Rate is not constant
Instantaneous Speed
Rate an object is moving at a specific time (at that instant)

8. Section 1: Describing Velocity
Velocity: speed in a certain direction
Example 25 mph East

9. Velocity: Direction Matters
Velocity Changes as Speed or Direction Changes
Velocity constant only if speed and direction do not change
Velocity changes if speed or direction changes

10. Velocity: Direction Matters
Combining Velocities
Resultant Velocity
Combine the velocities if the velocities are in the same direction
Subtract the smaller velocity from the large velocity if traveling in opposite directions

11. Section 1: Graphing Motion
Graph Motion on a Line Graph
X-axis: Time Y-axis: Distance
The slope (curve of the line) is the speed
Steeper the slope the faster the speed
Slope = Rise/Run

12. Section 2: Slow Motion on the Planet Earth
How does the theory of plate tectonics explain the movement of Earth’s landmasses?
How fast do Earth’s plates move?

13. Earth’s Plates
Plates: Pieces of earth’s crust broken into these pieces
Theory of Plate Tectonics
Earth’s plates move slowly in various directions; this has caused the movement of continents
Why Do Earth’s Plates Move?
Currents within the mantle are caused by rising hot molten rock and sinking cooler rock
New material at fault lines also cause movement

14. Plate Movement
Plates move very slowly
Centimeters per year

15. Section 3: Acceleration
What kind of motion does acceleration refer to?
How is acceleration calculated?

16. What is Acceleration? Acceleration: rate of the chance in velocity
Could: Speed UP
Could Slow Down
Could be a change in DIRECTION

17. What is Acceleration? Calculating Acceleration
Acceleration = final speed – initial speed / Time
SUBTRACT initial (starting)speed from the final (ending) speed and DIVIDE by the time
Example: Initial speed 0m/s; Final speed 10m/s; Time 5 seconds
10-0 / 5 = 2m/s2

18. Acceleration: The Rate at Which Velocity Changes
Defining ACCELERATION
Acceleration: THE RATE AT WHICH VELOCITY CHANGES
Acceleration changes SPEED or TIME changes
Acceleration is also DIRECTIONAL changes

19. Acceleration: The Rate at Which Velocity Changes
Calculating Acceleration
Acceleration = final velocity – starting velocity
time it takes to change velocity
Acceleration expresses as m/s2

20. Acceleration: The Rate at Which Velocity Changes
Examples of Acceleration
Positive acceleration: velocity INCREASES
Negative acceleration (deceleration): velocity DECREASES
Acceleration would also change if direction changes

21. Acceleration: The Rate at Which Velocity Changes
Circular Motion: Continuous Acceleration
CENTRIFUGAL acceleration: acceleration that occurs in circular motion
Objects travelling in circular motion are always CHANGING velocity