1. Chapter 9 Motion

2. Energy Review Kinetic energy is the energy of motion. (moving) A ball rolling down an incline has kinetic energy. Potential energy is the energy of an object because of its position. (stored energy) A stretch rubber band has potential energy

3. Describing and Measuring Motion Key Terms: 1.Motion 2.Reference Point 3.International System of Units 4.Meter

4. Describing Motion An object is in motion if its distance from another object is changing. A train moving down the tacks in in motion. Are you in motion right now as you sit in your desk?

5. Describing Motion No, you are not in motion. Parts of you body may be in motion. (eyes, hands, etc) Because the your distance from you chair is not changing you are not in motion. An object is in motion if it changes position relative to a reference point.

6. Reference Point To decide if you are moving, use your chair as a reference point. Reference Point: a place or object used for comparison to determine if something is in motion. Good reference points are stationary object. (tree, building, etc) Give me some examples of when you have used reference points.

7. Relative Motion Depends on the Reference Point. You aren’t moving as you sit in your chair if the chair is your reference point. If you choose another reference point it might change. If you compare yourself to the sun then you are moving very fast as the earth moves around the sun.

8. Relative Motion Are the skydivers moving relative to the airplane from which they jumped? Are they moving relative to the ground? (p. 310) Are the skydivers moving if your reference point is on the ground?

9. Relative Motion Yes, the skydivers are moving relative to the airplane and to the ground. Yes, the distance between the skydivers and the ground is changing.

10. Section 1 Review 1. How do you know if an object is moving? 2. Why is it important to know if your reference point is moving? 3. Suppose you are riding in a car. Describe your motion relative to the car, the road, and the sun.

11. Section 1 Review 1. You know an object is moving if it changes position relative to a stationary reference point. 2. If your reference point is moving, you will find it difficult to determine which direction you are moving or even if you are moving at all. 3. You are stationary relative to the road. As long as your car is moving in a straight line, the sun does not appear to move much in a short period of time. So, it appears that you are almost motionless relative to the sun.