1. Describing and Measuring Motion
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2. Describing Motion
Motion is when the distance from another object is changing.
You can think of motion as movement.

3. Motion
To decide if there is motion, you must first establish a reference point.
A reference point is a place or object used for comparison to determine if something in motion.
Motion is detected if it changes position relative to a reference point.

4. Relative Motion There are many objects that can be reference points.
You can use your chair, the whiteboard, the smartboard, the door.
You can also use larger objects like the moon, planets, and sun.
You will always be moving according to the sun, the moon, and other planets.

5. Measurement
Scientists all over the world use the same system of measurement to be accurate.
The system is called the International Systems of Units, or SI for short.
To measure motion, scientists use meter to measure the length.

6. Speed
If you know the distance an object travels in a certain amount of time, you can calculate the speed of the object.
Speed is the distance the object travels per unit of time.
We use the equation:
Speed= Distance/Time
Don’t forget your m, cm, km or hr, s, min.

7. Average Speed
The average speed is calculated by dividing the total distance by the total time.

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

9. Velocity Velocity is the 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.
So you could say 25 mph eastward (eastward would be the velocity).

10. Graphing Motion You can show the motion of an object on a line graph.
You can measure the steepness of the line by calculating the slope.
Slope = Rise/Run

11. Acceleration Acceleration is the rate at which velocity changes.
In science, acceleration refers to increasing speed, decreasing speed, or changing direction.

12. Calculating Acceleration
To determine the acceleration of an object moving in a straight line,, you must calculate the change in speed per unit of time.
Acceleration= Final speed – initial speed/time