Calculating Power of a rotating shaft

by sailadayaway
Tags: power, rotating, shaft
sailadayaway is offline
Feb21-08, 10:11 AM
P: 1
Hi, it's been a number of years since I've even thought about physics, so this is a very simple question. I have a rig set up where I have a power source that is rotating a shaft. Attached to this shaft is a wheel with a string, I have this string going through a pulley in the ceiling, and pulling a hanging weight. What I need to do is calculate the power that I'm getting out of this device, I remember how to calculate work and power, but can't for the life of me figure out where the radius of the wheel comes into play, and the torque. Any help would be appreciated

Phys.Org News Partner Physics news on
Better thermal-imaging lens from waste sulfur
Scientists observe quantum superconductor-metal transition and superconducting glass
New technique detects microscopic diabetes-related eye damage
FredGarvin is offline
Feb21-08, 10:23 AM
Sci Advisor
FredGarvin's Avatar
P: 5,095
If you have the power, you can calculate the torque (neglecting friction) from:

[tex]P = T \dot{\theta}[/tex]

[tex]P[/tex] = Power
[tex]T[/tex] = Torque
[tex]\dot{\theta}[/tex] = Angular speed

Just make sure your units are consistent!

Register to reply

Related Discussions
Seals for a rotating shaft? 30k+ RPM motor? Mechanical Engineering 9
Rotating Shaft Advise Mechanical Engineering 6
Calculate shaft power on gas turbine General Physics 0
Increase efficiency of rotating shaft. Mechanical Engineering 4
rotating shaft and ball-surface life Mechanical Engineering 2