# Real world problem

1. Mar 4, 2008

### scampbel

I need to roll a 9000lb roll across the ground. It is 4.5 feet in diameter, and is 115 feet long. I am attaching the bold ends to apply torque to move it. I don't need to move it that fast. How much Torque would I have to apply to each end to roll this across a flat floor. Assume that all torque applied is used to roll the drum and nothing else slips or moves. I have a number, I am trying to determine if it is correct. I am coming up with roughly 158 lb/ft per end. Any help is greatly appreciated.

Thanks!
Steve Campbell

2. Mar 4, 2008

### FredGarvin

It's the basic

$$\Sigma{T} = I \alpha$$

Set your desired acceleration and calculate the required torque from that. That will be a higher number than the torque required to simply overcome friction to maintain a constant speed.

3. Mar 10, 2008

### minger

If he assumes constant velocity, then there is no acceleration though, and theoretically the needed torque would be zero. However, one of the main friction forces is from the body deforming.

I remember back from machine design that there are formulas to calculate deflection of spheres and cylinders based on various material parameters. But, even based on a known deformation, I'm not quite sure how to convert that to a friction coefficient.