1. Motion & Forces
Chapter 12

2. Frame of Reference All objects move relative to some reference point
What classifies something as moving or not?

3. Motion & Position Motion- changing position
Reference point - an object or group of objects that is considered to be stationary
Common reference points: Earth, sun, stars
Ex: When sun is used as reference point, Earth is moving

4. Earths Orbit It takes the Earth one year to orbit the sun
Planet travels 100,000 km/hr
This means that you are moving!
Motion is relative b/c it depends on the reference point with which an object is compared.

5. Distance vs. Displacement
Distance- length traveled
Displacement- distance and direction from starting point to ending point
P. 195

6. Speed How fast or slow an object moves; change in position over time
Speed= distance/time
Unit is m/s or km/hr
Real world connection: Music BPM (p. 197)

7. Average Speed Total distance/ total time= average speed
When would this be useful to you?

8. Instantaneous Speed Speed of object at one instant in time
Cars speedometer measures instantaneous speed, not average speed!

9. Graphing Motion
One way to represent an objects speed is to use distance vs. time graphs
A flat line on this graph indicates that the object is not moving
P. 197

10. 12.2 Velocity & Acceleration
Velocity- describes both the speed of an object and the direction of its motion
*If an object is moving relative to another object that is considered to be moving relative to the earth, the velocities of the objects combine*
Resultant velocity- overall velocity

11. Velocity Velocity in the same direction= add
Velocity in the opposite direction= subtract
See p. 198 Figure 12.8
Echolocation

12. Acceleration Velocity is constant if speed and direction stay the same
Acceleration- rate of change in velocity
Ex: speeding up, slowing down, changing direction
Acceleration- speed increases
Deceleration- slowing down, negative acceleration

13. Calculating Acceleration
Acc. = (Final Velocity-Initial Velocity)
time
Positive vs. Negative Acceleration
P. 200
Cheetah Connection

14. Graphing Acceleration
A flat line on this graph represents constant speed
P 201