A cubical block (side 2m) of mass 20kg slides on inclined plane lubricated with the oil of viscosity η=10−1Poise with constant velocity of 10m/s. Find out the thickness of the layer of liquid. (g=10m/s2)
A
4×10−3m
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B
3×10−3m
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C
2×10−3m
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D
1×10−3m
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Solution
The correct option is A4×10−3m We know that , Fv=ηAdvdz=ηAvh
Balancing forces along inlined plane, mgsinθ=Fv=ηAvh ⇒20×10×sin30∘=10−2×4×10h ⇒h=4×10−3m=4mm