2. Chapter 2-Linear Motion Motion is Relative

3. Is the book on your desk moving?

5. Relative Motion Everything in the Universe is moving. In physics, when we talk about the motion of an object, we are talking about its motion relative to a fixed point on the Earth unless stated otherwise.

6. Is the book on your desk moving?

7. Example-- You are sitting on a bus which is moving slowly at 5 miles per hour. How fast are you moving relative to someone standing on the sidewalk?

8. Right, you are moving at 5 miles per hour.

9. However, if we change out point of reference…. You are sitting on a bus which is moving slowly at 5 miles per hour. How fast are you moving relative to the bus?

10. However, if we change out point of reference…. You are sitting on a bus which is moving slowly at 5 miles per hour. How fast are you moving relative to the bus? Right---you aren’t moving at all.

11. Now--- Say you are walking backwards in the bus at 1 miles per hour and the bus is still moving forward slowly at 5 miles per hour. How fast are you moving relative to the bus now? How fast relative to a person on the sidewalk?

12. Now--- Say you are walking backwards in the bus at 1 miles per hour and the bus is still moving forward slowly at 5 miles per hour. How fast are you moving relative to the bus now? Relative to the bus you are moving at 1 mile per hour. Relative to a person on the sidewalk---4 miles per hour.

13. Primary Point When we discuss motion in this class, we are talking about motion relative to the Earth surface.

14. Check Point Send me an email so that I know you’re watching this PowerPoint. My email is seibert-cindy@wc235.k12.il.usseibert-cindy@wc235.k12.il.us Research and answer these questions: – How fast is our Earth spinning on its axis in miles per hour at a point on the equator? – How fast is our solar system spinning around the center of the Milky Way Galaxy? Please provide website links along with your answers.