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On a Ferris Wheel

  1. Apr 19, 2005 #1
    Q. A chemistry student with a mass of 75 kg is riding a steadily moving Ferris wheel. When she is at the top of the Ferris wheel, the normal force from the seat on to her body has a magnitude of 556 N.

    Q. What would the normal force be on the student at the top of the wheel if the wheel's velocity were doubled


    If the wheels velocity were doubled mv^2 / R increases by a factor of four, i.e

    Weight of the student = 75 kg * 9.81 = 735.75 N - Normal Force ( 556 N )

    = 179.75 N * 4 ( coz, it increases by a factor of 4 )

    = 719 N

    There fore Normal force = 719 N - 735.75 N = 16.75 N , is this correct!!!!!!!


    :confused:
     
  2. jcsd
  3. Apr 19, 2005 #2

    OlderDan

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    Your numerical answer is probably correct, but your "stream of consciousness" approach to solving problems is going to get you in trouble when solving more compex problems. Do yourself a big favor and resolve to never put an equal sign between two things that are not equal. As a case in point

    719 N - 735.75 N = 16.75 N

    Well, no. This statement is false. In truth

    719 N - 735.75 N = -16.75 N

    A negative normal force is in the realm of possibility in this problem, as long as there is a bar or belt to hold in the passengers. How do you know the answer is not negative?

    Also,

    Weight of the student = 75 kg * 9.81 = 735.75 N - Normal Force ( 556 N )

    You just wrote a contradiction. Ignoring for the moment the units that you left out, you said

    W = 75 * 9.81 = 179.75

    Since when was 75*9.81 = 179.75?

    Try rewriting your solution in such a way that every statement you make is true. If you say A = B, then make sure A in fact does equal B.
     
  4. Apr 19, 2005 #3
    Well, yes I understand my mistake ( a serious one maybe ), but

    'OlderDan' you need to tone down, your disagreement, and try to be softer at times if not always. Well can't complain, since this is a free forum, and with 'Older ppl' I can understand that, it happens with them.
     
  5. Apr 19, 2005 #4

    OlderDan

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    Tone down? You're kidding me right? Has it occured to you that nobody else responded to your post earlier in the evening because nobody else took the trouble to try to figure out what you were doing? My reply to you was made for your benefit- not mine. It was directed specifically to what you wrote, without making any judgements about your personality or demeanor. Had I wanted to be insulting, believe me I could have done a much better job.

    You don't know anything about me, or how I relate to people as a person or as an instructor. Until you do, I suggest you limit your comments to the physics.
     
  6. Apr 20, 2005 #5
    Yes, I would like very much to limit my comments to the physics itself. And yes, thank you very much for looking through the whole problem.

    I certainly would not be interested in how you would relate to, but please certainly don't give a negative impression.

    I know that this is a forum, and ppl like you are doing a gr8 job, by sparing their time here, trying to help others but at the same time, go off in a tangential direction , deviate from the actual stuff,and pass of nasty comments along with it. For instance
    "stream of conciousness" [ a very diginified philosophical taunt ]

    Well, by writing all this, I am just trying to make you aware of these little, so called,

    'mood disturbers' .

    I don't like to pursue this any further. Thanks a lot!
     
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