# Thread: Pysics question with math element

1. ## Pysics question with math element

Hi all

Im currently stuck with a question and would be very greatfull if anyone can help.

If a small VRO (verticaly rotating object) was moving at a rate of 10rpm (revelutions per minute) and consuming 10 volts of electricity and I wanted to use it to move a VRO witch is twice as big and needed to travel 20+rpm's could i do it using a gearshift mechanism like the one you find on mountain bikes and connected in the same way with eather a chain or a belt.

If this can be done what would be the mathematical formula for this.

Thank you for taking the time to read this and i hope you can help

2. ## As posed - neither a Physics nor a Maths question

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As posed - neither a Physics nor a Maths question.

In brief: insufficient information.

How big is the 2nd VRO? Twice the linear dimensions, or twice the mass of the 1st VRO or what? How big is big? What are the masses?

For that matter how "big" is the 1st VRO, and what shape is it? How is it oriented relative to its rotation axis etc, etc, etc. Ditto for the 2nd "bigger" VRO? - Basically what are the Moments of Inertia (Ismall, Ilarge) of the two VROs about their chosen axes of rotation?

Any idea of the "starting" friction, and resistance against motion (egs: air resistance, bearing friction) encountered once the assembly is in motion?

What is the rated power of the driving source/motor/whatever it is?

The phrase "consuming 10v of electricity" is meaningless, not to say erroneous ... nothing ever "consumes volts" ... . A driven power sink consumes Watts of electricity or Joules per second of electricity ie: energy per given time period.
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