# Help with Rotation around fixed axis

4. [PSE6 10.P.014.] Figure P10.14 shows the drive train of a bicycle that has wheels 67.3 cm in diameter and pedal cranks 17.5 cm long. The cyclist pedals at a steady angular rate of 73.5 rev/min. The chain engages with a front sprocket 15.2 cm in diameter and a rear sprocket 7.45 cm in diameter.

Figure P10.14

(a) Calculate the speed of a link of the chain relative to the bicycle frame.
m/s
(b) Calculate the angular speed of the bicycle wheels.
rad/s
(c) Calculate the speed of the bicycle relative to the road.
m/s
(d) What pieces of data, if any, are not necessary for the calculations? (Select all that apply.)
diameter of wheels
none of these
diameter of front sprocket
length of pedal cranks
angular rate
diameter of rear sprocket

The figure is found at : http://www.webassign.net/pse/p10-14.gif

I tried solving part a using v=rw, but I'm not sure how to use the formula since there are two radii given.

## Answers and Replies

Anyone know how to solve this problem?? I figured out that you have to get the radius of the front sprocket, and plug that into the v=rw formula. However, I still get a wrong answer.

umm. sounds like you might be thinking too hard about this one .

How are you trying to solve it? you don't really say anything about how you're applying the equations. What are you trying to find with v=rw and which numbers are you putting where? (might it have to do with the units being in RPM instead of radians per second?)