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# Is it correct that if an 8-inch diameter wheel was rotating at 1,000 RPM then the vehicle would be going 12 MPH?

I'm making an electric mountain board and I am trying to find what gear ratios work to get the speed I want. I don't know if my math is right and I was just checking.

## Discussions

Best Answer 10 years ago

Circumference is 25.13 inches, at 1000 rpm that's 2513 inches per minute, is 1,508,000 inches per hour, is 125,500 feet per hour, is 42,000 yards per hour, is 23.8 mph. You might have made an error on the circumference pi*D or 2*pi*R L

Answer 10 years ago

I know what happened. I was doing this at school with one of the crappy school calculators that you have to push the buttons hard to get it to work. I did 8*1.4 instead of 8*3.14.

Answer 10 years ago

GIve the man a banana !

10 years ago

43.161512027491408934707903780069 MPH To be exact

Answer 10 years ago

Err ?

Answer 10 years ago

- 2*pi*R //8*3.14= 25.12
- RPMS*25.12 //1000*25.12= 25120
- 60 minutes in a hour sooo... 25120*60= 1507200
- 12 inches in a foot sooo... 1507200/12= 125600
- 5820 feet in a mile (i think) so.... 125600/ 5820= 21.5807...

There we go!!Answer 10 years ago

5280 Feet in a mile.

Answer 10 years ago

Well I was way off. Could you show me how to calculate that?

Answer 10 years ago

it's a lesson in unit conversion. how far does an 8 inch wheel go in 1 revolution?> How many seconds in a minute? how many minutes in an hour? How many feet in a mile? basic stuff..you should be able to do.

10 years ago

No.