Physics
The force of friction between two surfaces will increase if:

Irregularities on both the surfaces are removed
A layer of lubricant is kept between the two surfaces
Air gap is created between the two surfaces
The two surfaces are pressed harder

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Physics
Solar eclipse will take place when

the sun is between the moon and the earth
the earth is between the moon and the sun
the moon does not lie on the line joining the sun and the earth
the moon is between the sun and the earth

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