Describing motion


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Describing motion

  1. 1. Chapter 11: MotionChapter 11: Motion Section 1: Describing Motion
  2. 2. MotionMotion Motion occurs when: ◦ an object moves a certain distance in a certain amount of time ◦ an object’s position changes
  3. 3. DistanceDistance Distance is how far something has moved Measured in METERS, km, cm, mm, etc.
  4. 4. DisplacementDisplacement Displacement is the change in position of an object Also measured in METERS, km, cm, mm, etc.
  5. 5. SpeedSpeed Speed is the distance an object travels over the amount of time it takes to travel Measured in m/s (meters per second) Speed (m/s) = distance (m) ÷ time (s)
  6. 6. Calculating SpeedCalculating Speed 1. After driving for exactly 60 seconds, you have driven 600 meters. What speed were you driving? 2. After driving for 1 hour, you have driven 72 kilometers. What speed were you driving? a. Calculate the speed in km/hr b. Calculate the speed in m/s
  7. 7. Constant & Changing SpeedConstant & Changing Speed Constant speed means an object does not speed up or slow down. Changing speed means an object gets faster or slower.
  8. 8. Average SpeedAverage Speed  We usually calculate the average speed: Average speed (m/s) = total distance (m) ÷ total time (s) Yesterday, John Doe ran 6 km in 30 minutes. Sometimes he sped up and sometimes he slowed down. What was his average speed? a. Convert 6km to m: 6km x 1000m/1km = 6000 m b. Convert 30 mins to sec: 30 min x 60sec/1min = 1800 sec c. Calculate avg. speed: 6000 m ÷ 1800 sec = 3.33m/s
  9. 9. Instantaneous SpeedInstantaneous Speed Speed can be measured at a certain point in time. For instance, if you are driving, your speedometer may read 30 mi/hr. You don’t have to drive for an hour for your car to know this – your speed is instantaneous.
  10. 10. Graphing SpeedGraphing Speed Distance and Time are variables! ◦ Independent Variable: time ◦ Dependent Variable: distance
  11. 11. Graphing Constant SpeedGraphing Constant Speed
  12. 12. Graphing Changing SpeedGraphing Changing Speed
  13. 13. Graphing Changing SpeedGraphing Changing Speed
  14. 14. Graphing Changing SpeedGraphing Changing Speed
  15. 15. VelocityVelocity Velocity is a measure of an object’s SPEED and DIRECTION. Velocity is measured by: velocity = displacement ÷ time v = d/t
  16. 16. Velocity & DisplacementVelocity & Displacement If you run around a circular track and end up in the same position you started, your displacement is 0. So is your velocity: v = 0/time, so v=0
  17. 17. Calculating VelocityCalculating Velocity 1. You walk down a winding road and end up 80 meters from your starting point. It took 1 minute and 20 seconds to walk from one end to the other. What was your velocity? 2. Was your speed greater or less than the velocity you calculated in #1?