A square plate of side 0.1 m moves steadily at a velocity of0.1 m/s through a thin layer of water of viscosity 0.01 poise. Theplate moves parallel to a large fixed plate, and the water forms auniform film between them. If a force of 0.002 N is required tomove the plate, what is the thickness (gap) of the water layerbetween the two plates?
Correct answer: D. 0.0005 m
- A. 0.1 m
- B. 0.05 m
- C. 0.005 m
- D. 0.0005 m
Explanation
For Couette flow F = η A v / d. Convert η = 0.01 poise = 0.001 Pa·s. A = 0.1×0.1 = 0.01 m², so d = η A v / F = (0.001×0.01×0.1)/0.002 = 5×10⁻⁴ m = 0.0005 m.
Last updated
About Fluid Dynamics
Fluid flow is described through speed, pressure and density, including steady flow and the equation of continuity for conserving mass. Bernoulli's equation relates pressure, speed and height, while fluid drag and terminal velocity explain why a falling object eventually moves at constant speed when drag balances its weight.
Practise Fluid Dynamics
363 free Fluid Dynamics MCQs from Physics, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Exams that ask Physics questions like this
Physics is on 13 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
Related questions
𝑣 = √2g (h1 − h2) 𝑠ℎ𝑜𝑤𝑠 𝑡ℎ𝑒
A ball floats on surface of water in a container exposed to the atmosphere. Will the ball remain immersed at its depth or will it sink or will it rise if the container is covered and the air is removed?
A big rain drop having terminal velocity of 32 m/sec is divided into eight equal rain drops terminal velocity of each small drop will be:
A big rain drop having terminal velocity of 32m/sec is divided into eight equal rain drops terminal velocity of each small drop will be
A body falling in vacuum with some speed then which of the following is true: