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Average acceleration of Suzie stopping with roller blades

  1. Dec 22, 2007 #1
    Suzie (of mass 52kg) is roller blading down the sidewalk going 36 mph. She notices a group of workers down the walkway who have unexpectedly blocked her path, and she makes a quick stop in 1.9 seconds. What is Suzies average acceleration? Answer in m/s^2. What force was exerted to stop Suzie? Answer in N.



    I had converted miles to meters and divided it by the time in order to get the average, but the answer was incorrect. and for the second question I had multiplied the average by the weight, but that was also incorrect.
     
  2. jcsd
  3. Dec 22, 2007 #2

    Doc Al

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    Staff: Mentor

    That part sounds right. Show exactly what you did.
    That's not quite correct.
     
  4. Dec 22, 2007 #3
    did you convert hours to seconds? Aavg = delta V / delta t; so what you did should work..
     
  5. Dec 23, 2007 #4
    I changed 36 miles per hour to .01 miles per second which converts to 16.09344 meters per second. I divided that by 1.9 which equals 8.470231579 as the average acceleration. Then for the second part 8.470231579*52 = 440.4520421 N as the force exerted. I'm pretty sure that is what I did.
     
  6. Dec 23, 2007 #5

    Doc Al

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    Your answers are perfectly correct. (Except for the unrealistic number of significant figures carried. Round off your final answers.)
     
  7. Dec 23, 2007 #6
    thank you!
     
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