1. Motion
Chapter 9

2. Keywords Motion Reference point International System of Units Meter
Speed
Average speed
Instantaneous speed
Velocity
Slope
Acceleration

3. Motion
An object is in motion if it’s distance from another object is changing.

4. Reference Points
A place or object used for comparison to determine if something is in motion
An object is in motion if it changes position relative to a reference point!
Reference Point

5. Relative Motion It’s all relative!
You may not be moving in relation to a desk.
You are moving quite fast in relation to the sun!

6. International System of Units (SI)
Scientists use the same system of measurement to communicate clearly.
Scientists use SI units to describe the distance an object moves.
Meter- The basic SI unit of length.

7. Speed
An object’s speed is the distance the object travels per unit of time.
If you know the distance an object travels in a certain amount of time, you can calculate the speed of the object.

8. Calculating Speed Speed = Distance / Time
A car travels 60 kilometers in one hour. What is the speed?
60 km / 1 hour
60 km / hour

9. Average Speed Usually, speed is not constant!
To find the average speed, calculate the total distance traveled by the total time.
A cyclist travels 32 kilometers the first two hours, then 13 kilometers the third hour.
Average Speed = Total distance / Total time
32 km + 13 km / 3 hours
45 km / 3 hours
15 km / hour

10. Instantaneous Speed
The rate at which an object is moving at a given instant in time.

11. Velocity Speed in a given direction.
When you know both the speed and direction of an object’s motion, you know the velocity of the object.

12. Graphing Motion
You can show the motion of an object on a line graph in which you plot distance versus time.
Distance is the Y axis and Time is X axis.
The steepness of a line on a graph is called slope.
Slope tells you the rate of change, or speed.
The steeper the slope, the greater the speed.

14. Acceleration The rate at which velocity changes.
In science, acceleration refers to increasing speed, decreasing speed, or changing direction.

15. Types of Acceleration
Increasing speed- When an object’s speed increases.
Decreasing speed- When an object slows down. Also called deceleration, or negative acceleration.
Changing direction- When the direction of an object changes, it is acceleration.

16. Calculating Acceleration
Acceleration = (Final speed – Initial speed) / Time
If a car accelerates to 70 m/s in 7 seconds, what is the car’s acceleration?
Substract the car’s final speed from the initial speed and then divide that number by time:
70 m/s – 0 m/s = 70 m/s
70 m/s / 7 s = 10 m/s2

17. Types of Acceleration Acceleration Deceleration s s t t
No Acceleration (Constant Speed)
Types of Acceleration s t