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Physics Problem. I must find time.

by afcwestwarrior
Tags: physics, time
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Aug30-07, 09:52 PM
P: 457
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.
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Aug31-07, 09:20 AM
HW Helper
P: 4,124
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.
Aug31-07, 09:35 AM
Sci Advisor
PF Gold
P: 39,682
?? 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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