Polar Coordinates

1. Sep 2, 2007

krnhseya

1. The problem statement, all variables and given/known data

A car P travles along a straight road with a constant speed v = 65mi/hr. At the instant when the angle theta = 60 degrees, determine the values of r (with dot above) in ft/sec and theta (with dot above) in deg/sec. (r = 100ft)

The picture has a car on highway and radius pointing diagonally from the origin which is on the field in "/" like this.

2. Relevant equations

Vr = r (with dot above)
Vtheta = r*theta(with dot above)
v = sqrt(((Vr)^2)+((Vtheta)^2))

3. The attempt at a solution

Vr = v cos theta and found Vr without a problem.
I tried to plug in v = 65mi/hr (converted to ft/sec) into 3rd eqn with Vr in order to find Vtheta. After that I substitude it into 2nd eqn since I know the radius. I got the theta value and converted to deg/sec from rad/sec but I am not getting answer.

What mistake have I made? :(

Thank you.

2. Sep 2, 2007

learningphysics

What is the position of the car relative to the origin, and what direction is it moving in?

3. Sep 2, 2007

krnhseya

wow, i just made the stupidest mistake ever...
i JUST realized that radius is NOT 100 hahaha
sorry about that! and thank you!