Units problem

  • Thread starter kostantina
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Homework Statement



So I am calculating torque and power for a disk of radius 0.5 m that is subjected to a force of 50 N at its periphery and is rotating at angular velocity of 100 rad/s. Find torque and power.[/B]


Homework Equations



Torque= radius x Force = 0.5m *50N = 25Nm

Power= dW/dt= F*w(omega)= 25Nm * 100 rad/sec .... WHy the solutions book has an answer 2500 Nm/s. Why did they ignore the radians. I was thinking to convert the radians into meters or something like that. What am I not understanding here?
 

Answers and Replies

  • #2
gneill
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Radians are a sort of "unitless" unit. They arise out of ratios of like units, such as the ratio of the circumference of a circle to its radius (with suitable unitless constants involved). So when they get mixed up with "real" units they have a tendency to disappear. So, rad*m = m, rad*kg = kg, and so on.
 
  • #3
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Thank you for the response. It makes sense now. Will do further research on this to make sure I understand.
 

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