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Math Help - Sledge on a slop problem -

  1. #1
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    Sledge on a slop problem -

    A ramp that is 3.25m long leads up to a platform which is 1.25m high. A cubic packing
    case of side length 1m that weighs 50kg stands at the top of the ramp. It is held in position
    by a rope held parallel to the ramp.
    (a) If the coefficient of static friction is 0.35, what is the tension in the rope?


    I am trying to understand the solution to this problem, but I don't understand the part where values of

     sin \theta = \frac{5}{13}

     cos \theta = \frac{12}{13}

    how were these values obtained?
    Attached Thumbnails Attached Thumbnails Sledge on a slop problem --screen-shot-2014-03-17-23.32.08.png  
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  2. #2
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    Re: Sledge on a slop problem -

    Quote Originally Posted by Tweety View Post
    A ramp that is 3.25m long leads up to a platform which is 1.25m high. A cubic packing
    case of side length 1m that weighs 50kg stands at the top of the ramp. It is held in position
    by a rope held parallel to the ramp.
    (a) If the coefficient of static friction is 0.35, what is the tension in the rope?


    I am trying to understand the solution to this problem, but I don't understand the part where values of

     sin \theta = \frac{5}{13}

     cos \theta = \frac{12}{13}

    how were these values obtained?
    How is sine obtained in a right triangle? What about cosine?

    If that doesn't make sense, draw a right triangle with leg lengths 5 and 12, and answer the following questions:
    (a) What is the length of the hypotenuse?
    (b) Consider the acute angle adjacent to the 12-length side. What is its sine? (You should not need a calculator for that.)
    (c) What is its cosine?
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  3. #3
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    Re: Sledge on a slop problem -

    Hello,

    thanks for your reply,

    I know it was derived from drawing out a right angled triangle, but I still dont understand what numbers to put in?


    As far as i can see, in only know the length of one side? v = 1?

    where did 5 and 12 come from in the first place?? Thats what i dont get
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  4. #4
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    Re: Sledge on a slop problem -

    Quote Originally Posted by Tweety View Post
    A ramp that is 3.25m long leads up to a platform which is 1.25m high. A cubic packing
    case of side length 1m that weighs 50kg stands at the top of the ramp. It is held in position
    by a rope held parallel to the ramp.
    (a) If the coefficient of static friction is 0.35, what is the tension in the rope?


    I am trying to understand the solution to this problem, but I don't understand the part where values of

     sin \theta = \frac{5}{13}

     cos \theta = \frac{12}{13}

    how were these values obtained?
    from what I can tell they are wrong.

    You're given the opposite side is 1.25, and adjacent side 3.25.

    opp/adj = 0.385

    a 5/12/13 triangle has opp/adj = 5/12 = 0.417

    so this ramp is not 5/12/13.
    Thanks from Tweety
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  5. #5
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    Re: Sledge on a slop problem -

    Quote Originally Posted by Tweety View Post
    Hello,

    thanks for your reply,

    I know it was derived from drawing out a right angled triangle, but I still dont understand what numbers to put in?


    As far as i can see, in only know the length of one side? v = 1?

    where did 5 and 12 come from in the first place?? Thats what i dont get
    5-12-13 is a ratio. Not absolute measures. So if you know the length of one side, you can use those ratios to find the other two sides.
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