 What is the principle and Law of Floatation? | Class 9 Science What is the principle and Law of Floatation? | Class 9 Science

Floatation Online Class 9 Science Notes –

What is Fluid?

• It is a substance that flows and it takes the shape of the container in which it has been stored.
• Example- Liquid and gases
• Hydrostatic- It is a study of fluid at rest.
• Hydrodynamics- It is a study of fluid at motion.

What is Thrust?

• It is a force which acts normally on the surface.
• It is perpendicular to the unit surface area of the liquid.
• It is measured in terms of Force ( Newton or kilogram-force)
• It is a vector quantity.

What is Pressures?

• It is the magnitude of the normal force acting to the unit surface area of the fluid.
• It is the thrust acting per unit area of the body.
• Pressure =Thrust/Area
• It’s measuring units are SI(Newton per square meter) or Pascal or bar or millibar.

Principle of floatation

When the body floats in the fluid, the weight of fluid replaced is equal to the weight of the body. And there are two forces acted on it.

• Weight acting downward.
• The upthrust acting upwards.

Law of Floatation

Law of floatation states that the weight W of an object equals the weight w of the liquid displaced by it.

It refers to the floating object displaces its own weight of the fluid in which it floats.

Equation

W=w

W-Fb (force up thrust) = w

Application of the principle of floatation

1 Ships-

Ships float in water although it is made of steel and iron which is denser. It floats because-

The volume of the ship is larger than the volume of material used in it.

The average density is less than the density of water as empty space in a ship contains air.

2 Submarine-

It sinks as it takes water in buoyancy tanks. It sinks because-

Upthrust is not changed.

The weight of the submarine increase with the inflow of water.

3 Balloons-

It floats in the air because

The weight of hot air or hydrogen-filled in it is less than the weight of air.

UP thrust is greater than its weight.

Upward force results in the balloon to rise.

Check out another article click on Force and Laws of Motion

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Tag: Floatation, Application of the principle of floatation, Principle and law of floatation, Class 9 Science

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