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Physics Problem. I must find time.

  1. Aug 30, 2007 #1
    1. The problem statement, all variables and given/known data
    You are on a train that is traveling 3.0 m/s (to the left direction) along a level straight track. very near and parallel to the track is a wall that slopes upward at a 12 degree angle with the horizontal. As you face the windoes (.90 m high), (2.0 m wide) in your compartment, the train is moving to the left. The top edge of the wall 1st appears at window corner A and eventually disappears at window corner A and eventually disappears
    at window corner B. How much time passes between appearance and disappearance of the upper edge of the wall.

    2. Relevant equations
    Time= distance/average speed

    3. The attempt at a solution

    I multiplied .90 and 2.0 and I got .18m and then I divided it by 3.0 and I got .06 s. This is way off. What do I need to do.
  2. jcsd
  3. Aug 31, 2007 #2


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    Homework Helper

    Why did you multiply the lengths?

    You need to find the horizontal distance travelled... draw a picture... how do the window and wall look right as the wall appears... and draw another picture right when the wall leaves...

    What is the total horizontal distance? Hint: it is more than 2.0m. you'll need a little trig. Once you get the distance, divide by velocity to get time.
  4. Aug 31, 2007 #3


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    Staff Emeritus
    Science Advisor

    ?? Even your multiplication is wrong: if the window has width 2.0 m and height 0.9 m, then it has area 1.8 m2- but that has nothing to do with the problem.
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