Science Buddies: "Ask an Expert"

I need my graph 2 be simpler. Q: how does the gear ratio affect the RPM of the wheels?; 3 groups of bicycles, 3 bikes in each grp. one chainrng for each grp, all different rear cogs, measuring rotations. it's hard to explain if you don't understand, but can U help?

What kind of a graph did you try? What did you plot against what?

In thinking problems through and how to represent them graphically or otherwise, it is very important that you make sure you have appropriate units so that you aren't comparing apples to oranges and getting mixed fruit.

RPM (revolutions per minute) and measuring gear ratios don't have the same units. RPM involves time while gear ratios (number of teeth on one gear to number of teeth on another) are dimensionless.

I'm sure this didn't answer your question directly; hoever, I hope it makes you think about the problem again. Try explaining your problem to a parent or somebody else. The process of trying to explain something to somebody often triggers people to come up with the solution. If you can't explain it to somebody else, they you probably don't really understand it yourself.

The ratio of gear teeth in the driving and driven shaft will give you the absolute ratio of RPM between the driving and driven shaft. A bicycle with multiple driving and driven gears will give you a very large number of RPM ratios. For example, a driving gear with 90 teeth and a driven gear of 30 teeth will be a ratio of 3.0 to 1. When the driving gear is turning at 10 RPM, the driven gear is at 30 RPM. I don't know what you are trying to graph, but perhaps a data table with the driving gears on the horizontal and driven gears on the vertical is what you are trying to represent.

Rick Marz