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Kinematics

Kinematics. Types of Quantities. Almost all quantities have units - examples: meters, seconds, kilograms - Without units numbers would be meaningless Vector – Quantities that includes both magnitude and a direction Vectors can be drawn They are represented by arrows

cathleen-monroe
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Kinematics

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  1. Kinematics

  2. Types of Quantities Almost all quantities have units - examples: meters, seconds, kilograms - Without units numbers would be meaningless Vector – Quantities that includes both magnitude and a direction • Vectors can be drawn • They are represented by arrows Example: 12 m south Scalar – Quantities that do not include direction (magnitude only) Example: 4 seconds • http://www.youtube.com/watch?v=A05n32Bl0aY

  3. Distance vs Displacement • Distance is a scalar quantity: direction doesn’t matter • Displacement is a vector • Direction matters • Straight line route from where you started to where you end (as the crow flies) • MUST HAVE A DIRECTION

  4. What is the Distance traveled? 2 m 1 m 6 m 8 m d = 8 m + 6 m + 2 m + 1 m d = 17 m

  5. What is the displacement? - 2 m 1 m 6 m 8 m

  6. How can we interpret distance-time graphs? Do Now: Mark off a distance of 5 m on the floor and time how long it takes a ball to roll the distance. Repeat this three different times with three different speeds.

  7. Ball # Distance (m) Time (s) 1 2 3 Speed (m/s) Calculate the speed of each ball Now graph distance vs. time for each ball Distance (m) Time (s)

  8. Slope Find the slope of the three lines = = = df =final distance di = initial distance tf = final time ti = initial time

  9. Do you notice anything special about the slope of a line on a distance-time graph? It is equal to the speed or velocity = average velocity The physical significance of the slope of a distance-time graph is average velocity!!!

  10. Distance (m) Time (s) Describe the motion that this graph is representing Slope is constant Since slope = speed, speed is constant Slope is positive Therefore speed is positive (forward) The red car is moving with a greater velocity and therefore has a greater slope

  11. Distance (m) Time (s) Describe Slope is zero, therefore velocity is zero In other words, the object is at rest

  12. Calculate the velocity 300 Distance (m) 0 30 Time (s) = -10 m/s

  13. Distance (m) Time (s) Describe the motion that this graph is representing Slope is constant Since slope = speed, speed is constant Slope is negative Therefore speed is negative (backward)

  14. Describe the motion: Const. vel. forward At rest Const. vel. backward B C 50 40 Distance (m) 30 20 10 D A 1 2 3 4 5 6 Time (s) for: Calculate What is the: Total distance Total displacement 100 m 0 m

  15. B C 2 1 0 -1 -2 Distance (m) Time A E D , • Where is the velocity zero? • Where is the velocity constant? • Where is the ball moving forward? • Where is the ball moving backward? • What is the total distance traveled? • What is the resultant displacement? , 6 m -2 m

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