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Do Now

Do Now. Read and annotate the reading passage. Answer the questions on the back. January 22, 2013 Unit 3 Day 11 Distance, Displacement, Speed, and Velocity. Frame of Reference. Coordinate frame within which to measure position, motion, or other properties of an object. OR...

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Do Now

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  1. Do Now • Read and annotate the reading passage. Answer the questions on the back.

  2. January 22, 2013Unit 3 Day 11Distance, Displacement, Speed, and Velocity

  3. Frame of Reference • Coordinate frame within which to measure position, motion, or other properties of an object. • OR... • Observational frame tied to the motion of an observer. • In Newtonian physics, all motion must be defined in terms of a reference frame. • Relative Motion

  4. Frame of Reference • Is the speed of the ball different relative to the pitcher, the truck driver, and the jet pilot? Why or why not?

  5. 0 1 2 3 4 5 6 7 8 9 10 cm Distance • Distance (d) – how far an object travels. • Does not depend on direction. • Imagine an ant crawling along a ruler. • What distance did the ant travel? • d = 3 cm

  6. 0 1 2 3 4 5 6 7 8 9 10 cm Distance • Distance does not depend on direction. • Here’s our intrepid ant explorer again. • Now what distance did the ant travel? • d = 3 cm • Does his direction change the answer?

  7. 0 1 2 3 4 5 6 7 8 9 10 cm Distance • Distance does not depend on direction. • Let’s follow the ant again. • What distance did the ant walk this time? • d = 7 cm

  8. Displacement • Displacement (x) – difference between an object’s final position and its starting position. • Does depend on direction. •  means change in • Displacement = shortest distance from start to finish • In order to define displacement, we need directions. • Examples of directions: • + and –; right and left • N, S, E, W (north, south, east, west)

  9. Displacement vs. Distance • Example of distance: • The ant walked 3 cm. • Example of displacement: • The ant walked 3 cm EAST. • An object’s distance traveled and its displacement aren’t always the same!

  10. - + 0 1 2 3 4 5 6 7 8 9 10 cm Displacement • Let’s revisit our ant, and this time we’ll find his displacement. • Distance: 3 cm • Displacement: +3 cm • The positive gives the ant a direction!

  11. - + 0 1 2 3 4 5 6 7 8 9 10 cm Displacement • Find the ant’s displacement again. • Remember, displacement has direction! • Distance: 3 cm • Displacement: -3 cm

  12. - + 0 1 2 3 4 5 6 7 8 9 10 cm Displacement • Find the distance and displacement of the ant. • Distance: 7 cm • Displacement: +3 cm

  13. An athlete runs around a track that is 100 meters long three times, then stops. What is the athlete’s distance and displacement? Distance = 300 m Displacement = 0 m Why? Displacement vs. Distance

  14. Speed • Speed (s) – Rate at which an object is moving. • speed = distance / time • s = d/t • Like distance, speed does not depend on direction.

  15. 100 m Speed • A car drives 100 meters in 5 seconds. • What is the car’s average speed? • s = d/t • s = (100 m) / (5 s) = 20 m/s 1 s 2 s 3 s 4 s 5 s

  16. Speed • A rocket is traveling at 10 km/s. How long does it take the rocket to travel 30 km?

  17. Speed • A racecar is traveling at 85.0 m/s. How far does the car travel in 30.0 s?

  18. Velocity • Velocity (v) – speed with a direction. • velocity = displacement / time • v = x / t

  19. - + 0 1 2 3 4 5 6 7 8 9 10 cm Pulling It All Together • Back to our ant explorer! • Distance traveled: 7 cm • Displacement: +3 cm • Average speed: (7 cm) / (5 s) = 1.4 cm/s • Average velocity: (+3 cm) / (5 s) = +0.6 cm/s 1 s 2 s 3 s 4 s 5 s

  20. Scalar and Vector Quantities • Scalar Quantity – has magnitude but not direction. • Distance and speed are scalar quantities. • Vectors – have magnitude and direction, usually represented as an arrow. • Displacement and velocity are represented using vectors.

  21. Independent Practice • David walks 3 km north, and then turns east and walks 4 km. • Amy runs 2 miles south, then turns around and runs 3 miles north. • Jermaine runs exactly 2 laps around a 400 meter track.

  22. Independent Practice • A whale swims due east for a distance of 6.9km, turns around and goes due west for 1.8km, and finally turns around again and heads 3.7km due east. What is the total distance traveled by the whale? What is the displacement of the whale?

  23. Independent Practice • The speedometer in every car also has an odometer that records the total distance traveled • If the odometer reads 0 at the beginning of a trip and 35 km 30 mins later, what is the average speed of the car? • If the odometer reads 25 km at the beginning of a trip and 52 km at the end of the trip 65 mins later, what is the average speed of the car?

  24. Independent Practice • Pg. 25 # 1 – 8 • Pg. 26 # 26 – 27 (a, b)

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