# Polar Coordinates of a car

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!