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View Full Version : Tricky Kinematics Problems - Desperately need help!


RPierre
Oct14-08, 01:05 AM
1. The problem statement, all variables and given/known data
I am new to this board, but I am at my wits end trying to solve this problem. If anyone could provide a somewhat detailed solution i would forever be in debt, thanks!

One car, located at position (-29.9 , 0 ) is travelling at 12.7 m/s ( +x)
Another Car, located at position ( 0, -41.0) is travelling at 6.5 m/s ( +y)

+y Direction
^
|
|
----------> + x direction

Calculate the smallest distance between the two cars

2. Relevant equations

I created two functions :
p1 (t) = 12.7t - 29.9
p2 (t) = 6.5t - 41.0

Which represent the position of the cars, based on time, relative to the origin




3. The attempt at a solution

Using pythagorean theorom, i concluded the distance between them can be summarized as

d^2 = (p1(t))^2 + (p2(t))^2

Then i Attempt to solve the minumum of this function, which is where i always screw up.

The correct answer to the problem is 22.9 m
1. The problem statement, all variables and given/known data



2. Relevant equations



3. The attempt at a solution

tiny-tim
Oct14-08, 05:06 AM
Hi RPierre! Welcome to PF! :smile:
I created two functions :
p1 (t) = 12.7t - 29.9
p2 (t) = 6.5t - 41.0

Which represent the position of the cars, based on time, relative to the origin

Using pythagorean theorom, i concluded the distance between them can be summarized as

d^2 = (p1(t))^2 + (p2(t))^2

Then i Attempt to solve the minumum of this function, which is where i always screw up.

Well, that's fine so far. :smile:

Show us how you tried to solve it, and then we'll be able to see where the problem is. :wink: