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Fluid Friction

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What is Fluid Friction?

Fluid friction is a force that restricts the movement either within itself or of another medium moving through the liquid. Due to the movement of the molecules inside the fluid, internal friction occurs, and how the fluid interacts with other matter, external conflict occurs. It describes the friction between the layers of the viscous liquid that moves relative to each other. The internal resistance to flow is termed as viscosity. The less-dense the fluid, the greater is the ease for movement or frictional force. Fluid friction is mostly used in water slides so that we can prompt or slide down gently.


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State the Law of Fluid Friction

The laws of fluid friction are:


The rules hold differently for different lubricants.


It is indirectly proportional to the temperature of the lubricant.


The friction force is independent of the substances of the bearing surfaces as well as the load.


What are the Five Examples of Fluid Friction?

Some of the examples of fluid friction are:

The air particles that form up the air. It causes a falling object to slow down.


The lubricants used in hinges.


Submarine moving through water. It is external fluid friction that occurs on it.


When you drop any object in a fluid, the extent of its splash depends on its fluid friction.


The viscosity of honey is another type of example of fluid friction.


Types of Friction

There are five different types of friction:

Dry Friction 

It restricts the motion of two concrete surfaces in contact.

Fluid Friction  

It resists the movement of viscous fluids relative to each other.

Lubricated Friction 

It separates two solid surfaces by a lubricant fluid.

Skin Friction 

It is a drag component, resisting the movement of fluid against the surface of the body


What are the Factors Affecting Fluid Friction?

The factors on which fluid friction depends are as follows:

The Speed of the Body: 

Speed and friction are directly proportional to each other. The more the rate will be, the more the drag will be. For instance, a body moving with higher velocity will have more drag then a body moving with comparatively lesser speed.


Nature of the Fluid: 

The thinner the fluid, the lesser the fluid friction will be, and vice versa. For instance, water is thinner than honey. That is why there is less fluid friction in water than honey.


The Viscosity of Fluid: 

Fluid friction is directly proportional to the thickness of the liquid. The more the density, the more the drag will be.


The Shape of the Body: 

Other figures feel more drag than the body with a streamlined shape which begins and ends in points like the shape of a fish.


The Temperature: 

It is directly proportional to the fluid friction. Hence, with an increase in temperature, the fluid friction increases.


The Surface Area of the Body: 

The size of the body which faces the fluid should be as less as possible to feel less drag and so that it can cut through the fluid easily. For instance, a horizontal moving body can cut through the liquid more easily than a body moving vertically.


Solved Examples

Give a reason why objects must have unique shapes to move in fluids.


According to the laws of fluid friction, it is directly proportional to the shape of an object. In order to reduce fluid friction, special forms have been designed to minimize the opposing frictional force acting on them. These unique shapes are termed as streamlined shapes which are pointed at the ends, to cut the fluid smoothly.


What is a Viscous Drag?

Viscosity is defined as “resistance to flow”. Let’s consider pipe flow for the sake of illustrating an example. In fluid mechanics, any fluid directly in contact with a different medium moves at the same speed as that medium ). In the case of pipe flow, the tube is stationary, yielding a fluid velocity along the pipe walls of zero. The fluid velocity gradually increases with increasing distance from the pipe wall towards the center of the pipe, at which the rate is at maximum.


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So, since the flow velocity is 0 at the pipe wall, and V at the center of the flow, there must be some force holding it back, right? That’s viscous drag in action, the magnitude of which determines how much energy is required to maintain a given flow rate.


Fluid Friction - Law, Examples, Types, Factors Affecting and Solved Examples.

The conflict and the friction that is found in between the layers of a viscous fluid is Fluid Friction. Internal friction occurs due to movement of molecules that are inside the fluid and Viscosity  is the internal resistance flow, commonly known as the ‘thickness’ of a fluid. External conflict happens when we see how the fluids interact with one another.


Fiction can be of several types:

Dry friction resists the motion of two solid surfaces which come into contact.


Fluid friction occurs between the layers of a viscous fluid that are moving relative to each other.


Lubricated friction When a lubricant fluid separates two solid surfaces, it is said to be a case of Lubricated friction.


Skin friction is a component of drag, and is when a force  is trying to resist the  motion of a fluid across the whole body surface.


Internal friction is the force  which, while going through deformation, tries to resist the  motion between the elements that make up a solid material while it undergoes deformation.


There are some factors that affect Fluid Friction

  1. Object Design - Objects with a particular and specific design are helpful in order to be able to reduce the  friction by allowing fluid molecules to travel through the  body of the objects. Take the example of fish -  for the fish to swim , they have a  specific and streamlined body.

  2. Object Speed - The higher the speed of the object, the greater will be the friction.  Friction and Speed are directly proportional to one another . A body that moves with a higher velocity will definitely have more drag than a body which moves slowly, and has a reduced speed.

  3. Object Size - If the object is large,  the resistive force will be greater. A blue whale will encounter more friction when it is compared to a man swimming.

  4. Fluid Nature - Fluids which seem to have a  high inner resistance are said to have lots of fluid friction. Things, when  dipped in honey, have a harder time flowing through it than water since honey is much thicker than water.

Last updated date: 04th Jun 2023
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FAQs on Fluid Friction

1. How Does Fluid Friction Occur?

In a fluid, each particle of the fluid puts a force on the particles around it, and if one of those particles starts to move, the others will try to pull it back, thereby advancing and causing a cascade of interactions between particles. Eventually, the liquid encounters something substantial and as the liquid tugs on the tangible object, the atoms or molecules that make up the solid can’t reasonably separate from each other. So the liquid must move the entire concrete object if it even can. If this solid is rooted somewhere, it exerts a force back on the liquid, in another form of fluid friction.

2. How is Fluid Friction Minimized?

Ionizing the fluid can be one option as a similar charge will help us to some extent to minimize friction but isn’t a practical solution. On an experimental basis try to reduce the viscosity(the forces that fight against the free flow of liquid) of fluid by chemical means or by diluting it or by varying its temperature depending upon how your fluid reacts to those changes. To lower the friction in a tube or pipe, you can use rotation. In super cool liquids, the variance is minimized. It can also be minimized by giving unique streamlined shapes to the body, to reduce the drag according to laws of fluid friction.

3. Explain what Viscous Drag means?

The resistance of a fluid to flow is Viscosity  and is one type of friction that is seen in fluids, and  a force which is exerted on any  moving object by the fluid is referred to as a Viscous drag. We have seen how the different fluids flow. From pouring a glass of water to watching maple syrup creep towards the edge of a stack of pancakes. Viscosity is the essential, intrinsic inclination required for a  fluid to flow under any applied force.

4. What are the three Laws of fluid friction?

Following are the Laws of Fluid Friction:

The First Law says that the friction of the fluid will increase with the increase in the area of contact between the surface and fluid.

The Second Law says that the fluid friction will increase when there is an increase in the gradient of velocity of the substance.

The Third Law states that the fluid which has a higher coefficient of fluid friction will have a higher value of the fluid frictional force.

4. What do you mean by Fluid Friction?

Fluid friction can be said to be the  force which opposes a motion  within the fluid,  or in between where the fluid is, and through another medium that flows through it. Internal friction occurs as a result of interactions between the fluid molecules and exterior friction occurs due to how a fluid interacts with other things and objects. Fluids are made up of molecules  which are separated by a large amount of free space when they are examined under a high-powered microscope.

6. Give some examples of Fluid Friction?

Examples of Fluid Friction are as follows:

If we see a wet surface between two thin glass plates, we  will notice that the plates tend to get stuck and the plate at the bottom does not  fall when we hold only the template on top.

We  see that the lighter dust particles move faster when on the surface of a flowing river. This happens because of the high-velocity gradient which we see at the top layer of the water which is because of the lower dynamic fluid friction at that layer.

A submarine that is moving through water is the example of external fluid friction which occurs on it.

7. How can we minimize Fluid Friction? 

Giving certain streamlined shapes to the objects which move through the fluids. Fluids pass through moving objects in a swift manner when any object with a streamlined shape moves very fast. This reduces Fluid Friction. Trying to reduce the viscosity of the fluids by the use of certain chemicals, by trying to dilute it or even  by changing its temperature, the friction can be minimized. We will need to figure out how the fluids react to these changes.