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Motion, Speed, Velocity, and Acceleration!

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Motion A change in position, over time, relative to a reference point.

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So, What’s a Reference Point Thumb/Wall Example Carwash Driving/Truck What we compare all other movement or locations to! Often Earth Features Large Objects

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Reference Point Scenarios Suppose you are in a train, and you cannot tell if you are stopped or moving. Outside the window, another train is slowly moving forward. What could be happening? Your train is stopped, and the other train is moving slowly forward… The other train is stopped, and your train is moving slowly backwards… Both trains are moving forward, with the other train moving a little faster… Your train is moving very slowly backward, and the other train is moving slowly forward… Could you be sure as to which is actually happening??

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Reference Point Examples

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Speed Position can change at different rates Distance an object moves in an amount of time Formulas Distance / Time S=D÷TD=T·ST=D÷S 30mph; 15 cm/year; 500 m/s

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Suppose there’s a TORNADO that’s 1 mile wide, and it’s going 40 mph… What else is important?!?!? It’s Direction! Velocity is a Speed in a Direction! 15 Mph Northwest; 200 m/s South; 40 cm/ms Left Velocity

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Resultant Velocity The sum of all of the velocities of an object! (How Fast The Object REALLY is Moving…) Bus Runner Introductions:

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Resultant Velocity 5 m/s East What is the Runner’s Resultant Velocity?? (How fast is he REALLY moving??) 5 m/s East

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What About Now?? 5 m/s East What is the Runner’s Resultant Velocity?? (How fast is he REALLY moving??) 2 m/s East 7 m/s East

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What About Now??? 1 m/s West 5 m/s East What is the Runner’s Resultant Velocity?? (How fast is he REALLY moving??) 4 m/s East

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What About Now??? (Last One) 5 m/s West 5 m/s East What is the Runner’s Resultant Velocity?? (How fast is he REALLY moving??) 0 m/s

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Acceleration Change in Velocity over time Remember: Velocity is Speed AND Direction “Speeding Up” = Acceleration (Positive #) “Slowing Down” = Deceleration (Negative #) Turning (Change in Direction) = Acceleration

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Study each car above CAREFULLY! 1. Which car(s) undergo an acceleration? 2. Which car experiences the greatest acceleration? 3. Which line from the position/time graph below corresponds to each car?

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Calculating Acceleration THIS IS TOUGH!!! Final Velocity – Initial Velocity Time V final – V initial T V f – V i T V T

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Acceleration Problem #1! Mrs. Willever trips on a curb and starts sliding down a hill with a velocity of 1m/s south. After 3 seconds, her velocity is 7m/s south. What is Mrs. Willever’s acceleration? Final Velocity – Initial Velocity Time 7 m/s – 1 m/s 3s 6 m/s 3s 2 m/s s 2 m/s 2

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Acceleration Problem #2! You are walking down the street when you see an enormous, 112kg pickle rolling towards you at 9 m/s. You are, of course, surprised by a pickle of this size, let alone the fact that it is rolling down the street. You jump in front of it and begin pushing on it until you finally bring it to a stop 45 seconds later. At this point you are arrested for interfering in the “World’s Largest Pickle Rolling Championships”. Determine the acceleration of the pickle. Final Velocity – Initial Velocity Time 0 m/s – 9 m/s 45 s -9 m/s 45 s -1 m/s 5 s -1/5 (or -0.2) m/s 2

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Practice! At the top of your notebook paper, please write the following formulas: Speed/Distance/Time Formulas: S=D÷TD=T·ST=D÷S Acceleration Formula: Final Velocity – Initial Velocity Time

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