Name: History of a Barometer
Uploaded: 2019-07-19
Duration: 4 min 12 s
Description: A barometer is a scientific instrument measuring air pressure in a certain environment. Do you want to know how it came into the picture? Watch this video.

Question

What is law of floatation? Name an instrument developed on the basis of law of floatation.

Accepted Answer

When an object is placed in water two forces acting on it are

Weight ( $W$ ) of the object which acts downward and buoyant force by water ( $F_{b}$ ) which acts upward. Now let us check the below cases.

(a) $F_{b} > W$ : In this case, greater upward force brings the body in upward directions like cork and wax. These materials move upward and go above the surface of the water.

(b) $F_{b} = W$ : In this case, upward and downward forces are the same. And the body remains in equilibrium and floats in the water. Does not move upward or downward like wood and plastic mug filled with water.

(c) $F_{b} < W$ : In this case, greater downward force brings the body downwards and the body sinks like stone, an iron nail.

The law: The object placed in liquid only floats if the weight of the displaced portion of the liquid by immersed portion of the body is greater than or equal to the weight of the body. This is the law of floatation.

Hydrometer is the instrument that works on this law. It is used to measure the density or relative density of the liquid.

What is law of floatation? Name an instrument developed on the basis of law of floatation.

Important Questions on Archimedes' Principle and Floatation

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