1. Acceleration & Gravity January 26, 2016 7 th grade Chapter 3.3-3.5, part 1

2. Meme Moment

3. Motion Motion: the position of an object is changing compared to another object Molecules are constantly in motion

4. Reference Points If you are in a car on the highway, how will the motion of these look different? A car travelling the same speed as you A car passing you A car on the opposite side of the highway Lampposts on the side of the road

5. Speed vs. Velocity Speed = distance ÷ time Velocity = speed and direction o Can be shown as + or -, or a direction like “east” Average speed = all of the distance ÷ all of the time Instantaneous speed = speed at that exact time How do we show changes in speed & velocity?

6. Acceleration Acceleration: the rate at which velocity changes. Base units are m/s 2 Normal person: Acceleration is speeding up. Scientist: Since velocity is speed and distance, a change in acceleration can involve: Increasing speed Decreasing speed Changing direction

7. Examples of Acceleration A ball hits a wall and bounces back An airplane gains speed for takeoff When you’re on a ferris wheel, sometimes you’re moving faster in the up/down direction than forward/back

8. Calculating Acceleration Acceleration = (final speed – initial speed) ÷ time A roller coaster accelerates from 4 m/s to 22 m/s in 3 seconds. What is the average acceleration? (22 m/s – 4 m/s) ÷ 3 s = 18 m/s ÷ 3 s = 6 m/s 2

9. Gravity If you drop something from an airplane, it will fall faster and faster until it reaches a certain point It is getting faster, so it’s accelerating It’s accelerating because of gravity On earth, gravity is always ~10 m/s 2 o It changes if you’re really high up (9.81 m/s 2 vs 9.79 m/s 2 in Flagstaff) On the moon, gravity is ~1.6 m/s 2