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Math Help - newton's fundamental laws

  1. #1
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    newton's fundamental laws

    A puck of mass 30g slides across rough ice, experiencing a frictional force of 0.2N. If it was moving at 10 km/h when it hit the ice patch,

    a) how long did it take to stop?
    i first calculated the acceleration of the puck and i got 6.66m/s^2. then i determined the time and i got 1.5 s

    b) how long was the ice patch?
    i used the time calculated in part a and got the answer 2.08m

    please help...i thought this was a simple question but my answers do not reflect the answer key in the textbook...
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  2. #2
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    Quote Originally Posted by checkmarks View Post
    A puck of mass 30g slides across rough ice, experiencing a frictional force of 0.2N. If it was moving at 10 km/h when it hit the ice patch,

    a) how long did it take to stop?
    i first calculated the acceleration of the puck and i got 6.66m/s^2. then i determined the time and i got 1.5 s

    b) how long was the ice patch?
    i used the time calculated in part a and got the answer 2.08m

    please help...i thought this was a simple question but my answers do not reflect the answer key in the textbook...
    Fnet = ma => -0.2 = (0.03) a => a = .....

    Now apply the usual formulae for straight line motion under constant acceleration, using the data:

    a) u = 10km/hr = .... m/s (you know why the conversion from km/hr to m/s is required and how to do it, right?)
    v = 0 m/s
    a = ...
    t = ?


    b) u = 10km/hr = .... m/s
    v = 0 m/s
    a = ...
    x = ?
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  3. #3
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    Good textbook for study physics

    I use the textbook

    Conceptual Physics
    Rainyland(Cocomartini) BookStore -University Textbooks Campus Reference Books - Book Details

    to study the fundemental physics. I believe that will also useful for you to study physics

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  4. #4
    MHF Contributor Mathstud28's Avatar
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    Quote Originally Posted by checkmarks View Post
    A puck of mass 30g slides across rough ice, experiencing a frictional force of 0.2N. If it was moving at 10 km/h when it hit the ice patch,

    a) how long did it take to stop?
    i first calculated the acceleration of the puck and i got 6.66m/s^2. then i determined the time and i got 1.5 s

    b) how long was the ice patch?
    i used the time calculated in part a and got the answer 2.08m

    please help...i thought this was a simple question but my answers do not reflect the answer key in the textbook...
    The biggest thing I want to impart on you is this...in High School Physics...each chapter there is one formula that EVERYTHING is bulit off of...every problem is a derivation of that original formula...obviously for the chapter you are currently on it is F=ma...but for mechanical kinetic engery it is Ke_1+U_{g_1}=Ke_2+U_{g_2}...identify that formula each chapter and all the problems become easier
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  5. #5
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by Mathstud28 View Post
    The biggest thing I want to impart on you is this...in High School Physics...each chapter there is one formula that EVERYTHING is bulit off of...every problem is a derivation of that original formula...obviously for the chapter you are currently on it is F=ma...but for mechanical kinetic engery it is Ke_1+U_{g_1}=Ke_2+U_{g_2}...identify that formula each chapter and all the problems become easier
    This is very true, but don't forget the "synthesis problems." These are the ones that also depend on material from the previous chapters and really drive students nuts. (Which is one reason I like assigning them.)

    -Dan
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