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- Homework Statement
- A 12-in.-diameter circular plate is placed over a fixed bottom

plate with a 0.1-in. gap between the two plates filled with glycerin

as shown in Fig. P1.89. Determine the torque required to rotate the

circular plate slowly at 2 rpm. Assume that the velocity distribution

in the gap is linear and that the shear stress on the edge of the

rotating plate is negligible.

- Relevant Equations
- Torque=radius*(Viscous shear force) where viscous shear force is Fs

Fs = (shear stress)(area)

Torque = r(t)(a)

Hello all:) thanks for the help. This is for my fluids class. This is an example problem and I am stuck on it.

ok, so i found a video on youtube which walks through the entire process, but I am confused at a few sections. Here is the link to the video so you can follow:

at time stamp 2:37, he puts T=rta in differential form dT=rtdA

i don't understand why we need to do that? and why was area chosen to be the variable differentiated? why not r?

My biggest question though is why do we even need to make a diffeq? I am not seeing the reason why.

thanks much. its been a few years since i had diffeq

ok, so i found a video on youtube which walks through the entire process, but I am confused at a few sections. Here is the link to the video so you can follow:

at time stamp 2:37, he puts T=rta in differential form dT=rtdA

i don't understand why we need to do that? and why was area chosen to be the variable differentiated? why not r?

My biggest question though is why do we even need to make a diffeq? I am not seeing the reason why.

thanks much. its been a few years since i had diffeq