Question

Explain Fluid Friction

Important points in Fluid Friction

Example of fluid friction

With Diagram .

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Answer 1

FLUID FRICTION :-

The gases and liquids are called fluids. The friction exerted by fluid on an object is called fluid friction.

FACTORS ON WHICH FLUID FRICTION DEPENDS :-

1. The fluid friction of an object depends on it's speed with respect to fluid
2. It also depends on shape of the object
3. And nature of the fluid

EXAMPLES:-

1. sucking water through a straw
2. The movement of coffee as you stir it with a spoon
3. submarine moving through water

Answer 2

Explanation

⇒ If water in a tube is whirled and the of itself the motion of water stops after some time . this is very Common observation . what stops the motion ?

there is no external  force to stop it . A natural Conclusion is therefore that whenever there is relative motion between parts of a fluid , internal force are set up in the fluid . which oppose the relative motion between the part in the same way as force of friction operate when a block of wood is dragged along the ground . to maintain relative motion between layer of a fluid an external force is needed

" The property of a fluid by virtue of which it oppose the relative motion between its different layer is known as viscosity and the force that is involved is called the viscous force"

⇒ If F is the viscous force on the layer , then

⇒ F ∝ A where A is the area of the layer

⇒ $\sf F\propto -\dfrac{dv}{dx}$   The negative sign put to account for the fact that the viscous force is opposite to the direction of motion

⇒ $\sf F = -\eta A\dfrac{dv}{dx}$

Where  $\eta$   is a constant depending upon the nature of the liquid and is called the coefficient of viscosity and velocity gradient = $\sf\dfrac{dv}{dx}$