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Math Help - Help Please!

  1. #1
    Newbie
    Joined
    May 2009
    Posts
    1

    Help Please!

    hi
    i am trying to solve this question for someone, i think its calc. but i am have some problems, if you can help me out I would really appreciate.
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  2. #2
    Senior Member
    Joined
    Apr 2009
    From
    Atlanta, GA
    Posts
    409

    This is a physics problem

    By increasing in temperature, the steel expanded from 85 meters to S meters. Finding S given this increase in temperature is a physics problem. But here is the math:

    Suppose the track follows the curve of a circle of radius R, and central angle between the fixed point of the rail and the midpoint of the rail is \theta. Then S/2=R \theta. Similarly, 85/2=R\sin\theta. Solving this system of equations gives you all the information you need to find X. The vertical distance D between the ground and the center of the circle is D=R\cos\theta and X=R-D.

    Say for example, the rail expanded from 85m to 90m. Then the solution to \frac{90}{85}=\frac{\theta}{\sin\theta} is \theta=33.36^\circ. So the radius of the circle is 77.28m and the distance from the circle's center to the ground is 64.55m. Thus, the rail is sitting 12.72m off the ground. (Obviously, a realistic value of its expansion of a few millimeters will cause it to rise only a few centimeters.)
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