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Newton's law of viscosity: force or speed from the velocity gradient between layers

This type of question, asked 2 times: 25 Jun 2022, 29 Jan 2023. All 2 questions below, oldest first.

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  1. Question 1

    25 Jun 2022

    23
    The velocity of upper layer of water in a river is 36kmh−136kmh^{- 1}. Shearing stress between horizontal layers of water is 10−3Nm−210^{- 3}Nm^{- 2}. Depth of the river is ____\_\_\_\_ m. (Coefficient of viscosity of water is  10−2Pa.s)\left. \ 10^{- 2}Pa.s \right)

  2. Question 2

    29 Jan 2023

    120
    A metal block of base area 0.20 m20.20{\text{ }m}^{2} is placed on a table, as shown in figure. A liquid film of thickness 0.25 mm0.25\text{ }mm is inserted between the block and the table. The block is pushed by a horizontal force of 0.1 N0.1\text{ }N and moves with a constant speed. If the viscosity of the liquid is 5.0×10−3Pl5.0 \times10^{- 3}Pl, the speed of block is_____ ×10−3 m/s\times10^{- 3}\text{ }m/s.