In this post, we publish a bundle of Questions and answers related to Buoyancy and Buoyant force. Why does a stone sink but a wood float? A stone is denser than water. This means, if you compare the mass of a stone to the mass of the same volume of water, the stone’s mass will […]

# Fluids_21

## Difference between laminar and turbulent flow?

What is the difference between laminar and turbulent flow? The film of fluid that touches the container does not move because of friction with the container’s surface. But the fluid in the middle of the stream does. In laminar flow the transition from not moving to full-speed motion is continuous. Each thin film of water […]

## Difference between hydraulics & pneumatics?

Hydraulics deals with the use of liquid in motion, usually in a device such as a machine. Oil is the most common liquid used in pumps, lifts, and shock absorbers. Whereas hydraulics uses liquids to achieve mechanical advantage, pneumatics uses compressed gas. Since gases can be compressed and stored under pressure, releasing compressed air can […]

## Numerical problem based on Capillary Rise & Capillarity

Here, we will solve a Numerical problem based on Capillary Rise & Capillarity. Numerical assignment (on Capillary Rise & Capillarity) solved 1) A glass tube of radius 0.4 mm is dipped vertically in the water. Find up to what height, the water will rise in the capillary. If the tube is inclined at an angle […]

## Capillarity & Capillary Rise – definition & formula dervation

In this post, we have discussed capillarity and Capillary Rise. We also did the derivation of the formula of the height for Capillary Rise. We have added one assignment at the end of this post, that you must try (also check the solution – the link is provided) Capillarity If a capillary tube of glass […]

## Fluid flow – Important Formulas (for class 11)

This post presents a list of facts and formulas from the Fluid flow chapter of class 11 (grade 11) physics. formulas from the Fluid flow chapter of class 11 1 ) Pressure is the force per unit area exerted by a fluid on its surroundings: P = F/A Its SI units are pascals where 1 […]

## Difference between Cohesion and Adhesion & their importance

Cohesion refers to the attraction of molecules for other molecules of the same kind, but Adhesion is the attraction of molecules of one kind for molecules of a different kind. In this post, we will learn in detail what exactly Cohesion and Adhesion are, and this will help to understand the difference between them. To discuss these […]

## Specific gravity & Relative Density – are they the same?

A liter of water has a mass of 1.00 kg, but the same volume of methylated spirits has a mass of only 0.79 kg. We can say that the density of methylated spirits is 0.79 that of water. This is called its relative density (RD) or its specific gravity (SG). The two terms ( relative […]

## Comparing viscosities of liquids using a viscometer

The viscosities of liquids can be compared by observing their rates of flow through a glass tube. A simple device called a Redwood viscometer can be adapted easily for the laboratory. Comparing viscosities using a viscometer A viscometer is shown in Figure 1. Using the apparatus in Figure 1, fill the funnel with liquid to […]

## Weight Versus Buoyant Force – sinking, floating, & Buoying up

An object in a fluid will sink if the object’s weight is greater than the buoyant force (the weight of the fluid that the object displaces). An object floats only when the buoyant force on the object is equal to the object’s weight. An object is buoyed up until the part of the object underwater […]

## Solving Numerical problems on Archimedes’ Principle and Buoyancy

In this post, we will quickly revise Archimedes’ Principle and its legendary background. Then we will solve a few numerical problems in physics using this principle. Archimedes’ Principle and Buoyancy If an object is submerged in a liquid, the object displaces a volume of the liquid equal to the volume of the submerged object. There is […]

## Converting L atm to Joule | Litre Atm to Joule

Here in this post, we will convert L atm to Joule. L atm is also known as Litre Atmosphere. L atm to Joule L atm is the product of 2 units and these 2 units are Litre (unit of volume) and Atmospheric pressure (or atmosphere which is a unit of pressure). L atm, hence, is […]

## Numerical problem on car hydraulic braking – solving

In this post, we will solve a numerical problem based on the principle of a car hydraulic braking system. To solve this numerical, we will take the help of the concepts of the lever, and the pressure principle of Pascal. We will go through the problem statement first and then solve the numerical step-by-step. Numerical […]

## How to solve Numerical problems on terminal velocity

In this post, we will see how to solve numerical problems on terminal velocity. We will discuss the concept in brief and then take sample problem/s and solve them using the appropriate formula of terminal velocity. Theory & formula to solve terminal velocity numerical The first numerical problem in this post is about a spherical […]

## Deriving & Measuring viscosity using Stokes’ law

Here we will derive the formula of viscosity using Stoke’s law. We have already derived one expression of viscosity using the flow of a viscous fluid between two parallel plates. Now we derive a different equation of viscosity or coefficient of viscosity in terms of terminal velocity. When a sphere is released and allowed to […]

## How to use Pascal’s law to explain Hydraulic car brakes?

Pascal’s Law states that any change in the pressure applied to a completely enclosed fluid is transmitted undiminished to all parts of the fluid and the enclosing walls. Let’s see how Pascal’s principle is applied to design hydraulic car brakes. When the brake pedal is pushed, the piston in the master cylinder exerts a force […]

## Fluid Dynamics Class Notes for class 11 (includes viscosity) for ISC, CBSE, IGCSE boards

This post centers around the Fluid Dynamics Class Notes for class 11 (includes viscosity) for boards like ISC, CBSE, IGCSE, etc. A fluid is a collection of molecules that are randomly arranged and held together by weak cohesive forces and by forces exerted by the walls of a container. Both liquids and gases are fluids. […]

## Reynolds number & its formula, significance & sample numerical problem

The Reynolds number, Re is a dimensionless quantity and there is a ‘rule of thumb’ for flow in a pipe using the Reynolds number Re. When Re is less than 1000, flow can be taken to be laminar; when Re is greater than 2000, the flow will be turbulent. Reynolds number of a fluid flow […]

## Bernoulli’s Equation with derivation, explanation & examples

Bernoulli’s equation describes the relationship between pressure and velocity in fluids quantitatively. Hence, this equation is named after its discoverer, the Swiss scientist Daniel Bernoulli (1700–1782). Bernoulli’s equation states that for an incompressible, frictionless fluid, the following sum is constant: P+(1/2)ρv2+ρgh=constant, where P is the absolute pressure, ρ is the fluid density, v is the […]

## The Equation of Continuity with derivation & Streamlines of fluid flow

In this post, we will discuss two topics related to fluid dynamics. These topics are Streamlines and the Equation of Continuity with derivation. This physics tutorial is apt for class 11 physics for ISC, CBSE, IGCSE, and other boards (grade 11 and 12 for international boards). Streamlines The path taken by a fluid particle under […]

## Determination of Density of a solid and a liquid

Determination of Density of a Solid by Using a Measuring Cylinder Dividing the mass of a solid by its volume gives its density. The mass of a solid can be determined accurately by using a physical balance. The volume of an irregular-shaped solid can be determined by using a measuring jar (cylinder). To measure the […]

## How does Atmospheric Pressure vary with Altitude? show with a graph

As we go to higher altitudes such as top mountains the atmospheric pressure is found to decrease. The following are the reasons due to which atmospheric pressure decreases at higher altitudes: (i) Density of air decreases at higher altitudes.(ii) Height of the air column above us also decreases. A variation between the altitude and pressure/density […]

## How to derive Terminal Velocity equation using Stokes’ law (step by step)

Here we will work on the derivation of the Terminal Velocity equation or formula using Stokes’ Law. We will consider a situation where a solid sphere moving slowly in a fluid to derive the Terminal Velocity equation. We will also solve a numerical problem using the terminal velocity equation. Derivation of Terminal Velocity Equation using […]

## What is Stokes’ Law and what is the Formula for viscous drag?

Stokes’ Law and its formula: Eminent physicist Sir Stokes investigated fluid dynamics and came up with an equation for the viscous drag (F) on a small sphere at low speeds. This formula is now called Stokes’ Law. The Stokes’ Law formula is represented in this way: F = 6 πrȠV ………… (1)where r is the […]

## Buoyant Force formula with numerical problems

The upward buoyant force caused by Buoyancy is equal to the weight of the displaced fluid. Buoyant Force formula The magnitude of Buoyant force is expressed with the formula Fb = ρ g V where ρ is the density of the fluid, V is the volume of the fluid displaced, g is the acceleration due […]

## Archimedes’ principle and its statement and applications

Archimedes’ principle states that when a body is immersed partially or completely in a liquid, it experiences an upthrust, which is equal to the weight of the liquid displaced by it. This principle of Archimedes applies equally well to gases also. So the principle can be stated alternately as follows: Archimedes’ Principle states that when […]

## What Is Bernoulli’s Principle? Explain it with airplane wing and sails example

Bernoulli’s principle is named for Daniel Bernoulli, who presented it in 1738, and it concerns the relationship between pressure and flow speed in fluids. In its simplest form, Bernoulli’s principle states that increasing flow speed in fluids corresponds to decreasing pressure, and vice versa. Application of Bernoulli’s Principle – Airplane wings and Sails Airplane wings […]

## Viscosity – definition, derivation, coefficient of viscosity

Here we will define & discuss the concepts of viscosity and derive the formula of the coefficient of viscosity. When we pour a glass of water, it flows freely and quickly. But when we pour honey that flows slowly and sticks to the container. The cause behind this difference is fluid friction, both within the […]

## Buoyancy – Meaning, Definition, Buoyant Force, formula and Archimedes

We have certainly experienced Buoyancy knowingly or unknowingly. When we try to place a mug in a bucket of water we feel one opposing force coming upwards from water as we push the mug inside the water. Buoyancy is synonymous with that upward push provided by the liquid (water in this case). Similarly, when we […]

## Density & Relative density

Density is the mass per unit volume. The unit of density in SI is Kg/meter3. The relative density or specific gravity of a substance is the ratio of its own density and the density of water. It’s a number only without any unit. What is the difference between density and relative density? Density is the […]