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A plate of area 2m^(2) is made to move h...

A plate of area `2m^(2)` is made to move horizontally with a speed of `2m//s` by applying a horizontal tangential force over the free surface of a liquid. If the depth of the liquid is 1m and the liquid in contact with the bed is stationary. Coefficient of viscosity of liquid is `0.01` poise. Find the tangential force needed to move the plate.

Text Solution

Verified by Experts

Velocity gradient `=(2-0)/(1-0)=2 s^(-1)`

From Newton's law of viscous force,
`|F| =eta A (Delta v)/(Delta y)=(0.01xx10^(-1))(2)(2)=4xx10^(-3)N`
So, to keep the plate moving a force of `4xx10^(-3)` N must be applied.
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Knowledge Check

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