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This problem i have been trying to solve it for more than hours but i could not.

  1. Nov 21, 2008 #1

    A bowling ball is prevented from rolling down an incline of 30.0 dgree by a student pulling parrallel to the incline. Based on the known weight of the ball (W) determine the normal force that acts upon the bowling ball and the amount of force that the student has to exert. Neglect friction between bowling ball abd incline.
  2. jcsd
  3. Nov 21, 2008 #2
    If you were to draw the free body diagram, the diagram should have an arrow for each force.

    "A bowling ball is prevented from rolling down an incline of 30.0 dgree by a student pulling parrallel to the incline."

    This means that the student is pulling the ball, but only with enough force to prevent the ball from sliding down the inclide. The ball is not moving at all.
  4. Nov 21, 2008 #3
    But I did not get it please anyone can explain more for me.

  5. Nov 21, 2008 #4
    Well, the normal force is going to be equal to vector component of the weight that is perpendicular to the surface of the incline. So,

    N = W*cos(30deg)

    The force required to keep the ball from moving is going to be a little more difficult, but not too bad.

    First you have to find the component of the weight that is parallel to the surface:

    W // = W*sin(30deg)

    can you take it from here?
  6. Nov 21, 2008 #5
    Sorry I did not understand it because I have three W and how can I get the student force

    Thanks dimledur I apprerciate your help
  7. Nov 21, 2008 #6
    Did you draw a free body diagram? That would help follow my steps.
    W // = W*sin(30deg) is the force component that is parallel to the surface, this is what the student has to overcome.
  8. Nov 21, 2008 #7
    If I said that

    N=w because the ball is not moving. still I could not solve it because I need to know more information which let me to be able to solve it because I have two unknewn variables that are W and N
  9. Nov 21, 2008 #8
    you are able to relate w and n to eachother.

    Start by writing down everything you know.

    What is the normal force equal to?
    What is weight equal to?

    type it right here into the forums. if you don't know the answer, I'm sure you can easily look it up on google.
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