Question

Video project!

where you had to place a viscous fluid (like honey) between a book and a solid surface (ideally put the fluid in a bag or something similar so it doesn't get damaged) and then explore how easily the book slides across the table when you apply a force. It's also interesting to explore the effects of increasing the height of the fluid or using different fluids with different viscosities.

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Someone plz upload the video with an explanation or descriptive explanation

Thank you!

Answer 1

First of all, Let's understand what is viscosity. In simple terms, it is resistance to motion. Fluid with different viscosity behave differently. Mercury, honey has more viscosity than water. It means water flows easily but mercury and honey does not.

Now, Let's take an example of a boat rowing in water. The boat easily moves through water with the help of paddle and there is very less resistive force . However, if we replace water with honey or mercury or any viscous fluid, the boat will experience a large resistive force and velocity will decrease.

While talking about viscosity, we often talk about boundary layer. What is boundary layer ?? It is the layer of fluid just in touch with solid surface and its velocity is essentially zero. This is useful when we increase the height of viscous fluid.

Suppose we increase the height of fluid and now place the boat on viscous fluid, we will notice that boat moves with considerable larger velocity compared to before.

Why this happens ?

well, as move through the fluid from surface of contact to free surface, the velocity of layer increases . This is called as velocity profile. It means uppermost layer of fluid will have maximum velocity and lowermost layer will have least velocity.

Lesser the viscosity, more is the Reynolds number, means more is the velocity.

However, there are limitation. Air had low viscosity which put a lift on how steep the angle of take off for an aircraft be.

Let me know if you need more information.