Physics
It is easier to roll a stone up a sloping road than to lift it vertical upwards because

Work done in both is same but the rate of doing work is less in rolling.
Work done in rolling is more than in lifting.
Work done in rolling a stone is less than in lifting it.
Work done in lifting the stone is equal to rolling it.

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Physics
A white and smooth surface is

Bad absorber and good reflector of heat
Bad absorber and bad reflector of heat
Good absorber and bad reflector of heat
Good absorber and good reflector of heat

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Physics
RADAR is used for:

detecting and locating the position of objects such as Aeroplanes.
locating geostationary satellites.
receiving a signals in a radio receiver.
locating submerged submarines.

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