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Homework Help: Sliding down a roof

  1. Nov 1, 2007 #1
    1. The problem statement, all variables and given/known data
    a ball started at a height of 12.5 meters and rolled to the edge of a roof which is at 7 meters. Using a^2+b^2=c^2 we know it rolled a distance of 8.14 meters on the roof because it rolled a horizontal distance of 6m and a vertical distance of 5.5m. Find the time it rolled down the roof. The roof makes a 40deg angle with the horizontal and coeff of friction is .388.

    2. Relevant equations
    Potential E=KE+Ffriction
    mg*distance*sin(theta)=.5mv^2+(coeff of friction)*mgcos(theta)*distance down roof
    acceleration=g*sin(theta)-g*(coeff. of friction)*cos(theta)
    3. The attempt at a solution



    t=2.90 seconds
    Last edited: Nov 1, 2007
  2. jcsd
  3. Nov 2, 2007 #2
    What you have solved is for sliding down the roof whereas, the question has reiterated the term rolling. I think, question has been manipulated, in your own words!

    The attempt is correct, method-wise, if it is sliding. So, have you written 'sliding' incorrectly?
    If it is indeed 'rolling', one information is missing: information about the ball? Assuming a spherical ball (as most of them are), is it solid or hollow? Have you missed that?
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