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Calculating acceleration of ball rolling down ramp

  1. Sep 12, 2015 #1
    1. The problem statement, all variables and given/known data
    Hi, I know the acceleration of steel ball rolling down the inclined track is 5/7 * gsin(theta). But is it possible to find the acceleration of ball rolling on the inclined track just by using the distance travelled on the horizontal plane(attached to the Inclined track) and the time taken? Assuming constant velocity and no friction when rolling on the horizontal plane.

    2. Relevant equations

    vf^2 = vi^2 +2as -- 1
    v(diagonal) = v(horizontal)/cos(theta) -- 2

    3. The attempt at a solution

    As we know that the speed along the horizontal plane is constant, the velocity = distance/time. Assuming it travelled 1m in 1s, velocity = 1m/s.
    final velocity when ball reaches the end of ramp = initial velocity of ball at the start of horizontal plane
    thus, final velocity = v(horizontal)/ cos(theta) -- same as eq 2
    with the final velocity, we can use eqn 1 to calculate the acceleration assuming we have the length of ramp.
    Is this method correct? or am i missing something? this method will only work if assuming there is no loss of mechanical energy??
     
  2. jcsd
  3. Sep 12, 2015 #2

    ehild

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    Welcome to PF!

    Why do you think that the horizontal component of the velocity is constant?
     
  4. Sep 12, 2015 #3
    i know velocity is not constant as there is friction but what if we assume there is no friction action on the ball?
     
  5. Sep 12, 2015 #4

    ehild

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    Assume a piece of ice sliding down along an incline. There is no friction. Is the horizontal component of velocity constant?
     
  6. Sep 12, 2015 #5
    Im thinking yes. cos there is no force along the horizontal component hence velocity will be constant
     
  7. Sep 12, 2015 #6

    ehild

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    Gravity has no horizontal component, but there is the normal force N from the incline acting also on the piece of ice, or on the rolling ball. The normal force has horizontal component.
    normforcehor.JPG
     
  8. Sep 13, 2015 #7
    You need to consider the moment of inertia of the ball. That's why the acceleration of a ball
    would be different from that of a cylinder or a hoop.
     
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