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Can any one help with this Fluid mechanics question please? 
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#1
Jan813, 08:47 AM

P: 9

1. The problem statement, all variables and given/known data
A shaft of diameter 74.9mm rotates at 1400rpm in a bearing which is of diameter 75.03 mm and 75mm in length. The annular space between the shaft and the bearing is filled with oil of viscosity 0.096 kg/ms.By assuming a uniform velocity gradient in the oil, determine the power required to overcome the viscous resistance in the bearing. 2. Relevant equations F=μ(ωR/l)2∏RL Thats the equation i have been using, where l is the difference between the radius of the outer ring and inner ring (i.e. bearing and shaft) 3. The attempt at a solution When i plug in the values i get: 0.096* ((146.61*37.45*10^3)/0.065*10^3)*2∏*(37.45*10^3)(75*10^3) this gives 143.12N Presuming that this is all ok i then have no idea how to get to a power? thanks 


#2
Jan813, 09:10 AM

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Thanks
PF Gold
P: 6,521

How much torque would this force produce on the shaft when it is turning at 1400 rpm? Once you know the torque, you can find the power.



#3
Jan813, 09:22 AM

P: 9

Ah yeah thanks got the right answer :)



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