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What is friction and its types?

‘Friction‘ is a force that resists motion of sliding or rolling of one object moving relative to another. It is a result of the electromagnetic attraction between the charged particles of two touching surfaces.   Types of Friction Static Friction : It is defined as the frictional force that acts between the surfaces when they are at rest with respect to each other. The magnitude of the static force is equal in the opposite direction when a small amount of force is applied. When the force increases, at some point maximum static friction is reached. Rolling friction : It is the force that resists motion when an object rolls on a surface. Technically it’s not friction; its ‘rolling resistance’ since when a body rolls perfectly upon a surface, on paper, there is no sliding friction between that object and surface. Sliding friction : It is the frictional force between two surfaces that are rubbing against each other. It’s a very easy and common concept. It’s hard to find a perfectly sm
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Why is the Earth called Blue Planet?


“The Earth has almost 70% water on its surface due to which it looks blue in color”.

or

“More than 71% of the earth is covered with water. Hence, its is known as the blue planet”.

Why Earth looks blue from space?

The Earth has extremely hot red heat under its crust and the top outer surface is covered with water. The Earth’s surface has many oceans and seas starting from the Arctic Ocean to the Southern Ocean.

These oceans & seas cover almost 70% of Earth’s surface and the remaining 30% is covered with land. It means that almost 70% of Earth’s surface appears blue from outer space & the leftover 30% looks greenish-brownish. This is the reason why Earth looks blue from outer space.

 

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