1. Describing Motion Section 2-1

2. Motion Motion occurs when an object changes its position.Motion occurs when an object changes its position. Both Distance and Time are important in describing motion.Both Distance and Time are important in describing motion. Sometimes you know motion has occurred even if you didn’t see it happen. (mail truck)Sometimes you know motion has occurred even if you didn’t see it happen. (mail truck) Relative motion: you are moving even when you are sitting in your chair. You are moving relative to the other planets.Relative motion: you are moving even when you are sitting in your chair. You are moving relative to the other planets.

3. Distance vs. Displacement Distance: How far an object has moved (total)Distance: How far an object has moved (total) Displacement: How far and in what direction an object has moved from its start position.Displacement: How far and in what direction an object has moved from its start position. Figure 2 pg. 39Figure 2 pg. 39

4. Speed Speed = the distance an object travels in a given amount of timeSpeed = the distance an object travels in a given amount of time Speed = distanceSpeed = distance time time SI unit of speed is m/sSI unit of speed is m/s

5. Calculating speed Calculate the speed that you are running, if you run 400 meters in 72 seconds.Calculate the speed that you are running, if you run 400 meters in 72 seconds.

6. Types of Speed Constant speed: speed doesn’t change (set your car on cruise control)Constant speed: speed doesn’t change (set your car on cruise control) Changing speed: Riding a bike for 5 km. Take off and increase speed, slow down up hill, speed up down hill, stop for stop sign. The trip took you 15 min (.25 h)Changing speed: Riding a bike for 5 km. Take off and increase speed, slow down up hill, speed up down hill, stop for stop sign. The trip took you 15 min (.25 h) Average speed: total distanceAverage speed: total distance total time total time Instantaneous speed: speed at any given moment. Instantaneous speed: speed at any given moment.

7. Graphing motion Distance – time graphsDistance – time graphs Figure 5 pg. 43Figure 5 pg. 43

8. Velocity Velocity: includes speed and DIRECTIONVelocity: includes speed and DIRECTION Storm is moving at 20km/hr. Should you be seeking shelter?Storm is moving at 20km/hr. Should you be seeking shelter? Two trains could be going the same speed, but have different velocities.Two trains could be going the same speed, but have different velocities. Race car going around an oval track might have constant speed, but different velocities.Race car going around an oval track might have constant speed, but different velocities.