1. Chap 2 Motion and Speed

2. Motion Motion occurs when an object changes its position
You don’t always need to see something move to know that motion has taken place
To know whether the position of something has changed, you need a reference point. Ex: Mail truck
Relative motion- we are always in motion and are moving relative to the other planets in the solar system and the sun (30 km every sec.)

3. Distance Distance describes how far an object has moved
SI unit for length or distance is meter
Ex: 50 meter dash

4. Displacement
Displacement is the distance and direction of an object’s change in position from the starting point
Ex: page 39

5. Speed Speed is the distance an object travels per unit of time
Speed= Distance / Time or S=D/T
Units of speed are measured in meters per second or m/s
Rate- any change over time

6. Constant speed- never slows down or speeds up
Changing speed pg 41
Average speed- is the total distance traveled divided by the total time traveled
Instantaneous speed- is the speed at a given point in time. When something is speeding up or slowing down, its instantaneous speed is changing
Ex: driving a car in town, riding a bicycle

7. Equation for speed can be rearranged
T = D / S
Pg 42

8. Graphing Motion
A distance-time graph makes it possible to display the motion of an object over a period of time.
Ex: pg 43
The steepness of the line on a graph is called the slope

9. Velocity
Velocity is the speed of the object and the direction of its motion
The velocity of an object can change even if the speed of the object remains constant
Ex: pg 44

10. Motion of Earth’s Crust
Earth’s continents were once part of a single landmass called Pangaea
Formed over 250 million years ago
Began to separate into smaller pieces about 66 million years ago
Continents are still moving today

11. How do continents move?
Earth is made of layers: Crust, upper mantle make up the lithosphere
Lithosphere is broken into huge sections called plates that slide slowly on puttylike layers below. Similar to egg shell
These moving plates cause geological changes such as formation of mountain ranges, earthquakes, and volcanic eruptions
Plates speed varies between 1 to 17 cm per year