How Do You Calculate Power from Torque and Angular Velocity?

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SUMMARY

The discussion focuses on calculating power from torque and angular velocity using the formula P = T * ω. The motor operates at four revolutions per second with a torque of 20 Nm. The correct interpretation of frequency as angular velocity is crucial; thus, the angular velocity is calculated as ω = 4 * 2π, leading to a power output of 500 watts. Miscalculations arose from incorrectly applying the conversion of revolutions to radians.

PREREQUISITES
  • Understanding of torque (T) in Newton-meters (Nm)
  • Knowledge of angular velocity (ω) in radians per second
  • Familiarity with the relationship between frequency (f) and angular velocity
  • Basic proficiency in using power equations in physics
NEXT STEPS
  • Study the relationship between frequency and angular velocity in rotational systems
  • Learn about the implications of torque in mechanical systems
  • Explore the derivation and application of the power equation P = T * ω
  • Investigate real-world applications of power calculations in motors and engines
USEFUL FOR

Students in physics, mechanical engineers, and anyone involved in the design or analysis of rotating machinery will benefit from this discussion.

Pablo
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Homework Statement



Motor runs at a rate of four revolutions/sec has a torque of 20. What is it's power.

Homework Equations



T = (2π) / w
f = w / (2π)
w = 2πf

P = T * w
Power = Torque * angular velocity

The Attempt at a Solution


[/B]
T = 20 Nm
f = 4 * 2π = 8π
w = 2π * (8π) = 16π^2

P = 20 * (16π^2) = 3158 Watts

My answer is too big, and I am not sure what I am doing wrong.
 
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Pablo said:
f = 4 * 2π = 8π
w = 2π * (8π) = 16π^2
I think you're confusing frequency and angular frequency. You've ended up multiplying the given revolutions per second by 2π twice.

One revolution is 2π radians of angular displacement. So 4 revolutions per second is 4 x 2π radians per second and is the angular velocity, ω.
 
gneill said:
I think you're confusing frequency and angular frequency. You've ended up multiplying the given revolutions per second by 2π twice.

One revolution is 2π radians of angular displacement. So 4 revolutions per second is 4 x 2π radians per second and is the angular velocity, ω.
Ah okay, so when they say the frequency they mean the angular velocity right. So it'd be 500 watts.
 
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Pablo said:
Ah okay, so when they say the frequency they mean the angular velocity right. So it'd be 500 watts.
When they say "frequency" they mean "events per unit time". If the "events" in question happen to be rotations then you can interpret them as 2π radian angular displacements. From there you can calculate the angular velocity by multiplying the frequency by 2π.

Yes, 500 watts looks good.
 

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