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## math/physics problem

This is a discussion on math/physics problem within the General Off Topic+ forums, part of the QJ.net Forum Miscellaneous category; ok a dude runs 1/3 of a circle with a radius of 27 i figured out the circumfrence is about ...

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1. ## math/physics problem

ok a dude runs 1/3 of a circle with a radius of 27

i figured out the circumfrence is about 170

i need to find distance traveled and displacement

d traveled is 56 2/3

but how do i find displacement aka the length of a chord?

is there an easier way then graphing it and converting the d traveled to an arc length and then doing the distance formula between point A and B?

2. The only way I can think is:

c^2 = a^2 + b^2 - 2ab(cos C)

c = sqrt (27^2 + 27^2 - 2*(27^2)*cos(360/3))
-= Double Post =-
I get 46.8, sounds right?

3. i dunno but i figured out an easier way

he ran 1/3 of it

so the angle is 360/3 or 120... make a triangle and solve for the bottom cz its the one where the two sides are the same length...

4. 1/3 * (pi * 27^2) = 1/3 * (pi * 729) = pi * 243 = distance travelled around the arc

1/3 of a circle is 2/3 * pi radians... so if he starts at (27,0), he ends up at (27 * -.5, 27 * sqrt(3) / 2) or (-13.5, 27 * sqrt(3) / 2). [Note that the starting and ending points aren't really relevant, since the distance would be constant regardless of what point on the circle he started at.]

So the chord distance is the hypotenuse of the triangle with sides of length (27 - -13.5) and (0 - 23.27 * sqrt(3) / 2), or (40.5, 27 * sqrt(3) / 2). Which comes to sqrt(1640.25 + 546.75), or sqrt(2187), or about 46.7653718043596869252410 51220659 :P

So yes, you got it right. About 46.8 FTW.

5. I got 13.37 What class is this again?

6. college physics

bu these are baby problems compares to what my guy gives us on a daily basis.. u know where i am if u want an example

7. Originally Posted by BAWLS
i dunno but i figured out an easier way

he ran 1/3 of it

so the angle is 360/3 or 120... make a triangle and solve for the bottom cz its the one where the two sides are the same length...
That's what I did :)

You sure this is college level? This was taught to me when I was 16.

8. Yeah... definitely learned this stuff is 9th grade... when I was 15. College for me was calculus, calc 2, and linear algebra.

9. Moved to Smart talk.

10. smart talks....wotever >_>

11. yeah for some reason he gave us an easier worksheet today instead of bookwork... and i usually take 2-4 hours on 3-4 book problems

12. your back in school already? I don't go back until the 12th

13. This is just applied trig isn't it? I'm taking that this year.

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