please help

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mattflint50

Junior Member
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Apr 25, 2005
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60
the question is. A car traveling at 40 ft/s crosses a bridge over a canal 10s before a boat traveling at 20 ft/s passes under the bridge. the canal and the road are straight and at right angles to each other. At what rate are the car and boat seperating 10s after the boat passes under the bridge.

THis is how I did it but it turned out worng.

First I made a right triangle. Sinse the car was traveling at 40 ft/s and would travel for 30 sec I multiplied them to get 1200. I did the same for the boat and got 400. I then used the pathogream theorem to get the distance to be 1264.9. I then differentiated the theorem to get X dx/dt + Y dy/dt = Z dz/dt. I then plugged the numbers in and got dz/dt to equal 38.58 and it is the wrong answer.
 
mattflint50 said:
...Sinse the car was traveling at 40 ft/s and would travel for 30 sec....
Click to expand...
Your general methodology looks good, but where are you getting the thirty seconds?

Eliz.
 
mattflint50 said:
because it had been traveling for 10 seconds longer
but is that correct?
Click to expand...
Because what had been travelling longer than which? Is what correct? The thirty seconds? No.

Eliz.
 
Im not trying to be rude but I do not appreciate the way that you answer the questions that I ask. Please, if you are not going to answer them dont make me sound stupid. I stated right in thr problem that the car had been traveling faster. You are always the one who responds to my questions but you never answer them. So please stop.
 
I never argued with the stated rate of the car; I'm sorry I somehow gave you the impression that I thought you'd copied the exercise incorrectly, and would have no reason to think that you had.

You had asked where you had gone wrong in working the exercise, I complimented your methodology and gave you a hint (how did you go from "10 + 10" to "30"?) to help you find the slight error. I apologize.

Eliz.
 
no problem I found the answer to the problem, and the mistake. Sorry I became frustrated.
 
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