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JEE Main 2023 (29 Jan, Shift 2) · Viscosity & Stokes' Law

Viscosity & Stokes' Law question from JEE Main 2023 (29 Jan, Shift 2)

Q16JEE Main 2023 · 29 JAN · SHIFT 2Medium

Viscosity & Stokes' Law

A metal block of base area 0.20 m2^{2} is placed on a table, as shown in figure. A liquid film of thickness 0.25 mm is inserted between the block and the table. The block is pushed by a horizontal force of 0.1 N and moves with a constant speed. If the viscosity of the liquid is 5.0×10−3 Pl5.0 \times 10^{-3}\text{ Pl}, the speed of block is ____________ ×10−3\times 10^{-3} m/s.

Figure

Numerical answer type. Work it out, then open the answer.

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Answer: 25

  1. Constant speed, so applied force = viscous force: F=ηAvdF = \eta A\frac{v}{d}.
  2. v=FdηA=0.1×0.25×10−35×10−3×0.20v = \frac{Fd}{\eta A} = \frac{0.1\times0.25\times10^{-3}}{5\times10^{-3}\times0.20}
  3. v=2.5×10−510−3=25×10−3v = \frac{2.5\times10^{-5}}{10^{-3}} = 25\times10^{-3} m/s
  4. So the answer is 2525.
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