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Science Starter #17 2/12/10

Science Starter #17 2/12/10. Q: Jaime’s family was going camping. They parked their car and hiked 8 miles to the campsite. Write a description of their hike. Motion Quiz. Any questions from the homework? Any questions about Distance Displacement Speed Velocity v=d/t

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Science Starter #17 2/12/10

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  1. Science Starter #172/12/10 Q: Jaime’s family was going camping. They parked their car and hiked 8 miles to the campsite. Write a description of their hike.

  2. Motion Quiz • Any questions from the homework? • Any questions about • Distance • Displacement • Speed • Velocity • v=d/t • reading a distance vs. time graph

  3. The Domino Effect • Finish any remaining trials with your dominoes. • Create a graph of domino spacing (on the y-axis) vs. time (on the x-axis). • Turn in you lab paper (objective, hypothesis, data table, conclusion) and your graph.

  4. Conclusion Questions • How did the spacing between the dominoes impact the speed at which they fell over? • In general which spacing between dominoes (from the x-axis of your graph) resulted in the greatest toppling speed? • At the maximum toppling speed of the row of dominoes, how long a row of dominoes would be required to take 1 min to fall?

  5. Acceleration

  6. Acceleration • Acceleration – rate of change of velocity • Object changes its speed, direction, or both • Positive acceleration – object is speeding up • Negative acceleration – object is slowing down • Zero acceleration – object is moving at a constant velocity

  7. Calculating Acceleration • Acceleration = change in velocity time = vfinal – vinitial = vf – vi time t • Units = m/s – m/s = m/s2 s

  8. Example #1 • Suppose a jet airliner starts at rest at the end of runway and reaches a speed of 80 m/s in 20 s. What is its acceleration? a = vf – vi t = 80 – 0 20 = 4 m/s2

  9. Example #2 • A skateboarder is moving at a speed of 3 m/s and comes to a stop in 2s. Calculate the acceleration of the skateboarder. a = vf – vi t = 0 – 3 2 = -1.5 m/s2

  10. Reflection Q: How are velocity and acceleration related? Give examples of positive acceleration, negative acceleration, and no acceleration.

  11. Science Starter #182/16/10 Q: Find the average speed of a marble on a 2 meter long track if it takes 50 seconds to reach the bottom. If the marble’s velocity changes from 15 m/s at the beginning of the track to 30 m/s at the end, what is the marble’s acceleration? Remember to include direction and check units!!

  12. Graphing Acceleration • Velocity goes on the y-axis • Time goes on the x-axis • Slope = rise(y) = velocity = acceleration run(x) time • Upward slope – (+) acceleration – speeding up • Downward slope – (-) acceleration – slowing down • Flat line – 0 acceleration – constant speed

  13. Physical ScienceOlympics!!

  14. Reflection • What are 2 questions you still have about speed, velocity or acceleration? How will you get these questions answered?

  15. Is it possible for a hockey player to move a puck that is at rest on the ice without accelerating it? Why or why not? • Usain Bolt, an Olympic runner from Jamaica, set the world record for the 100 meter dash with a time of 9.58 seconds. He reached his maximum speed of 12.42 m/s (27.79 mph) in approximately 6.25 seconds. How much did he have to accelerate from rest (at the starting block) to reach his maximum acceleration? • Figure skater Mirai Nagasu starts with a speed of 4 ft/sec and accelerates to a speed of 10 ft/sec in 3 seconds to hit a triple axle.  How much did she accelerate?

  16. 4. What is the length of time for a hockey puck moving at 40m/s to reach the goal from approximately 25 feet away?  5. Austrian luger Manuel Pfister soared down the Whistler track (1,400 meters) in just 32.72 sec. How fast was he going? BONUS- convert his speed to mph.

  17. 6. In the 1932 Olympic Games, the 3,000 meter steeplechase was won by Volmari Iso-Hollo of Finland.  He ran 3450 meters in 10 min, 33.4 seconds.  (They ran an extra lap because the official made a counting error.)  What was his average speed in this race?

  18. 7. Draw a distance vs. time graph for the following events: The bobsled team starts off at rest, then quickly gains speed. After 15 seconds, the sled gets stuck on some sharp ice and they skid to a stop. The team jumps out for 4 seconds to free the sled. Then they get back in, gradually regain their speed for 1 minute (60 seconds), then coast at a constant velocity for the remainder of the race. They finish the 1450 meter race in 4 minutes and 30 seconds.

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