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Homework Help: Height equation in a weird way.

  1. Sep 25, 2010 #1
    1. The problem statement, all variables and given/known data

    A hot air balloonist forgot to calibrate his altimeter before taking off. The altimeter displays his height as A*h (A being a constant multiplcator, and h is his real height). He does not know A, nor does he know the speed of sound. How can he find his height with just two rocks that he can drop over a canyon and listen for their echoes. Neglect air resistance.


    2. Relevant equations
    y=y0+V0T+.5GT^2
    G=-9.81

    3. The attempt at a solution
    I assumed V0 and Y0 is equal to 0.
    Dt (difference in time) is equal to T2-T1
    I disregarded the speed of sound because it is a constant in both drops.

    First drop:
    y1=-4.905(T1)^2
    Second drop:
    y2=-4.905(T2)^2

    (Dhr)(difference in real heights) is y2-y1=

    -4.905(T2)^2+4.905(T1)^2

    If I record the heights the altimeter gives me at the two points, and find the difference and then divide that by my (Dhr), I should get my multiplication factor right? That is assuming the equation for the (Dhr) is right.
     
  2. jcsd
  3. Sep 25, 2010 #2
    The question doesn't ask you to find A so you figured out the problem already
     
  4. Sep 26, 2010 #3
    So I my equation for A (the multiplaction factor) is correct? It was right of me to disregard the speed of sound?
     
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