# Speed of a bicycle chain

1. Nov 1, 2009

### freeurmind101

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

A bicycle has wheels 67.3 cm in diameter and pedal cranks 17.5 cm long. The cyclist pedals at a steady angular rate of 71.5 rev/min. The chain engages with a front sprocket 15.2 cm in diameter and a rear sprocket 6.45 cm in diameter.

2. Relevant equations
v=rw

3. The attempt at a solution
I converted the revs/min to rad/s and then used that value times the radius of the front sprocket and got 1.138 m/s but this is wrong. I then tried to calculate the tangential velocity at the back sprocket with the same rate of pedaling and that radius and added it to the value I got from the front sprocket but this was wrong as well. Do i need to take into account the length of the pedal crank?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Nov 1, 2009

### Delphi51

Welcome to PF, Free.
Looks interesting, but there is no question. What are you trying to find?

3. Nov 1, 2009

### freeurmind101

Sorry lol, I forgot to include the question. (a) Calculate the speed of a link of the chain relative to the bicycle frame.

4. Nov 1, 2009

### Delphi51

The method sounds good, but I don't agree with the answer!
Can you show the details of the calculation so we can look for the error?

5. Nov 1, 2009

6. Nov 1, 2009

### freeurmind101

Wow, I just realized I forgot to divide the diameter by 2 to get the radius lol. I'm such an idiot lol.

7. Nov 1, 2009

### Delphi51

Ah, I knew it had to be some little thing. Easy to do!