## anonymous 5 years ago If you observed a car traveling at a constant rate around a circular track of 100 m diameter in 5 seconds, what is it's rate of motion in m/s? Then what would it be in miles/hour?

1. anonymous

A circle of diameter d=100m has a radius of d/2=50m As $v=\omega R$ and $\omega=2\pi f$ $f=1/T$ The period of the motion is the time taken for one circuit: T=5s So. $v=\omega R =2\pi fR= 2\pi R/T = (100\pi)/5 = 62.8ms ^{-1}$ which is 153 miles per hour. pretty fast.

2. anonymous

Thank-you, but I have one question. How come you didn't multiply the '2'? This is very helpful, and I am getting the same answer, but I am confused as to why the 2 isn't multiplied.

3. anonymous

The radius which is 100/2=50 but it is then multiplied by 2 again so goes back to 100. so 2R=100. does that help?

4. anonymous

Yes, thank-you very much. You've been very helpful.