- #1

ballboy

## Homework Statement

I am trying to figure out what torque is applied to 2 wheels counter-rotating at 4,000 rpm when a tennis ball is squeezed between them and then propelled forward (because the wheels are counter-rotating).This is how a tennis ball machine propels a ball forward. I know the distance between the edge of the counter-rotating wheels and I know how much force it takes to compress the tennis ball so it fits between the wheels, ie about 60 lbs, so I guess that's 30 lbs on each wheel. The traditional formula of Torque = Distance * Force * sin(theta) does not work because the force is being applied in line with the radius against the edge of each wheel towards the axle. Sin (0 deg) or sin (180 deg) in that equation are 0 so the equation yields 0 torque but that cannot be the case. It's kind of like applying breaks to the wheels of a car but not stopping. Radius of the wheel is 3".

Does anyone know? Maybe there is a way to translate perpendicular force against the wheel edge into tangential force when the wheel is rotating at a certain rpm?

## Homework Equations

Torque = Distance (ie radius) * Force * sin(angle)

## The Attempt at a Solution

Torque = 3 in * 30 lbs * sin(180) = 90 * 0 = 0

But it can't be zero and also doesn't the rpm figure in somehow?[/B]