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Average speed & average velocity Problem

  1. Oct 3, 2007 #1
    1. The problem statement, all variables and given/known data
    Brandon is climbing a mountain. He starts from an elevation of H1=511m above sea level. In 6.18 hours he climbs to an elevation of H2=2746m above sea level. The length of his path is L1=16000m.

    A)What is the average angle of ascent the path makes with the horizontal?Theta=
    B)What is his average speed along the path in meters/second? average speed=
    C)What is his average vertical velocity? Vup=
    D)After he eats he hikes back down to their starting point in T2=4.24 hours
    What is his average vertical velocity? Vdown=

    2. Relevant equations
    avg speed=total distance/total time
    avg velocity=v=Delta x/delta t
    tan theta=opposite/adjacent

    3. The attempt at a solution

    A)tan theta=opposite/adjacent
    Im so confused as to what equations to use.

    B)avg speed= total distance/total time


    C)avg velocity=v=Delta x/delta t

    D)Confused on D as well

    Please give some suggestions or the correct equations will be great.thanx Dave
  2. jcsd
  3. Oct 4, 2007 #2


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    Homework Helper

    You are on the right track. If you haven't done it already, one thing that helps is to draw a picture.

    For a, you have the correct equation. Hint: what does L1 represent in a simple idealized geometric shape?

    For c & d: be careful. The problem says average vertical velocity.

    Also, looks like you double posted by mistake.:smile:
    Last edited: Oct 4, 2007
  4. Oct 4, 2007 #3
    Hotvette thanx alot for the help just got a few more questions.

    If your talking in terms of a triangle L1 would represent my hypotenuse I believe. So would 16000m be my hypotenuse is what your suggesting. But dont I have to choose the equation involving the hypotenuse to find the angle. Like:

    sin theta= opp/hyp
    cos theta= adj/hyp

    But my question is what is the equation for vertical velocity?

    Thanx Vette
  5. Oct 4, 2007 #4


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    For the angle yes, use:

    sin theta = opp/hyp

    average vertical velocity = vertical displacement/time
  6. Oct 4, 2007 #5
    Thank you learn,

    But im wondering if my hyp=16000m and im trying to find theta. whats my opp or how do i find my opp.?
  7. Oct 4, 2007 #6


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    What distance does he travel vertically? they give you initial height and final height...
  8. Oct 4, 2007 #7
    Thanx Learn,

    Ok so if I subtract the H2=2746m- 511m=my distance is 2235m

    So to find theta I did this:

    sin theta=opp/hyp

    sin theta=2235m/16000
    theta=7.98 degrees or 8 degrees

    Please tell me this is correct
  9. Oct 4, 2007 #8


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    yup, looks right to me. But I get 8.03 degrees.
  10. Oct 4, 2007 #9

    For my average speed =total distance/total time,do I use the 16000m for total distance/6.18hrs or do i convert hrs to seconds. Since my answer has to be in m/s?
  11. Oct 4, 2007 #10


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    Yeah, I think converting to s is best. otherwise your answer will be in m/hr... best to use m/s.
  12. Oct 4, 2007 #11
    Question so if vertical speed= deltaV/T,would my deltaV= .705m/s?I got .705m/s from my average velocity equation which was 16000m/22680s=.705m/s for avgV. Is average vertical velocity and vertical velocity the same equation?
  13. Oct 4, 2007 #12


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    vertical velocity is vertical displacement which you know is 2235m divided by time.
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