word problem

[swimmer3]

If lance was using his 210-millimeter-diameter chainring and pedaling at a rate of 85 revolutions per minute, what diameter sprocket would he need in order to maintain a speed of 45 km per hour?

Can you walk me through this prblem step by step? I am completely lost.

 

[tkhunny]

The first step would be to tell us the diameter fo the tire.

One way to proceed might be to translate everything to linear velocity.

 

[swimmer3]

diameter of tire is 700 mm

 

[tkhunny]

210*pi mm / revolution * 85 revolution / minute = 17850*pi mm / min

45 km / hr = 700*pi mm / revolution * X revolution / minute

There is very little remaining to do.