# Circular motion with an angle

1. Homework Statement
the question is to find the angle that should be banked on a highway curve. the velocity is given, which is 100km/hr and the radius is 300m

2. Homework Equations

3. The Attempt at a Solution
i know i need to convert the units first, but then i dont know what to do... to find the angle, i need to use tangent to find it, or is it?? if yes, i dont know how...
plz help...tmr is the physics final...thx a lot~~XDXD

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I can't remember if you end up getting a tangent or not, though you will probably end up with tan or cot. If you draw a careful freebody diagram, and use Newton's 2nd law properly then you can get through this problem.

the equation i got is that $$\tan\theta=\frac{v^2}{rg}$$. i dont know how i got this equation, but it did give me a right answer. can u help explain it?

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I think you end up with mgsin0 = mv^2/r
0 = theta

if you draw a freebody diagram you should see that it is that component which creates circular motion. if i'm wrong i apologize but i'm 85% sure. :P

no...it should be tan, coz i got the right answer from my equation. i just dont understand how i can get the equation on #3

i think it depends on where you're counting the angle from.

draw a freebody diagram of the vehicle on the banked turn, the perpendicular component to the car's motion is the Fc. you can write it in terms of Fg and an angle.

cristo
Staff Emeritus