Chapter 3 Describing Motion

Motion How would you describe motion? Why is it important to know about motion?

Motion Motion is a change in position. Do you need to see something move to know motion has taken place? Give an example.

Motion is relative Suppose you’re sitting in a moving car. As you look outside, trees and buildings are flying by. Is there a reference frame where you are not moving? If your frame of reference is the car than it would appear that you were not moving.

Reference How do we know something has changed its position? We know something has moved based on it’s position to a reference frame. A frame of reference is a group of objects that are not moving relative to one another. http://www.youtube.com/watch?v=MI8TUOtZ5Z0 http://www.youtube.com/watch?v=6Vfed1idHyU&NR=1&feature=fvwp

Displacement Displacement is the distance and direction of an object’s final position from its initial position. In other words… How far where something ends up compared to where it started and in what direction it is.

Displacement Displacement can be described using a vector. -Vectors have both size and direction.

Distance Distance is how far something has actually travelled. Mini-Pride Drill example. How is this different from displacement?

50 yds and back? Distance:50+50=100 Dsplcemnt:0-0=0 50 yds, stops at 30 on way back? Distance:50+20=70yds Dsplcemnt: 30-0=30yds