1. Measuring Motion How do you know where you are, if you are moving, and how fast?

2. Reference Point When deciding if an object is moving, we are actually comparing that object to another that appears to be staying in place. Motion is defined as when an object changes position over time relative to a reference point. We give the object a direction, up, down, left. Right, north, south, etc.

3. Common reference points These can include nonmoving items like buildings, trees, mountains, etc. Moving objects like other cars, birds, etc. can also be reference points.

4. Speed Defined: The distance travelled by an object divided by the time taken to travel that distance. Since most objects do not travel at a constant speed, we calculate average speed: average speed=total distance total time

5. Speed on a graph Graphs can help us recognize speed and changes in speed as an object moves.

6. Velocity Velocity is the speed of an object in a particular direction. Speed and velocity do not mean the same thing. An object’s velocity can only stay constant if its speed and direction remain constant. If speed or direction changes, the velocity changes also.

7. Combining velocities If two objects are going in the same direction, we add them together to get the resultant velocity. If two objects are going in opposite directions we subtract the smaller velocity from the larger velocity. The resultant velocity is always in the direction of the largest velocity.

8. Acceleration In science, unlike its common meaning, acceleration means the rate in which velocity changes over time. An object is said to have accelerated if its speed, direction, or both change. A decrease in acceleration is called negative acceleration or deceleration. Acceleration is not only how nuch the velocity changes but also how fast it changes.

9. Calculating Average Acceleration We can use the equation: Average acceleration= final velocity-starting velocity time it takes to change velocity Velocity is expressed in meters per second(m/s) time in seconds (s) Acceleration is expressed in meters per second per second (m/s/s)

10. Acceleration on a graph It is easy to spot positive and negative acceleration on a graph. Acceleration graphs will be line graphs since it involves time. If the line goes up, the object is accelerating. If it goes down, it is decelerating. The shape of the line will tell how quickly the acceleration or deceleration is taking place.

11. Circular Motion An object travelling in a circle is always changing direction so it is always changing its velocity. Therefore, according to the definition, it is accelerating. We call circular motion acceleration centripetal acceleration. Examples are the blades of windmills, ferris wheels, the moon orbiting the Earth.