Why a white roof Keep a house cooler as compared to black roof?
This is due to the process of reflection of heat rays. White colour has capacity to ret heat rays & absorbs less heat as compared to black colour.
That is why while roof keep a house cooler as compared to black roof.
Explain why we perspire before rain?
The occurs due to greater quantity of moisture in air, before raining there is a large amount of moister in air which causes us to perspire before rain.
Why fanning produces cooling effect in body?
This is due to the process of evaporation, which has cooling effect. When a fan is starts the moving air increases evaporation, which produces cooling effect in body.
Explain why a thick glass tumbles cracks when very hot water is poured into it?
This occurs due to the process of expansion. When hot water is poured into a glass troubler or jug it causes expansion of inner surface & uneven expansion breaks enter layer.
The earth bulges out at the equator, why?
This is due to the shape of the earth. The earth is not a true sphere but it is an ellipron. The equatorial diameter of the earth is 12756.2711 km. While it’s polar diameter is 12713.5 km. The difference between its equatorial & polar diameter is about 43 kilometers the rotation the earth on its axis produces as centrifugal force which increases its equatorial diameter.
Due to this reason the earth bulges at the equators.
Why the sun appears red at the time of sunset & sunrise?
This occurs due to scattering of light by small particles of dust & smoke near the surface of the earth. At the time of sunset and sunrise light rays have to cover a travel of greater distance. Soduring their travel dust & smoke scatters all others colors of light except red & red light rays travel unhindered & reach to use, that is why sun appears red.
Why meat takes long time to cook on the mountains?
This occurs due to air pressure. The relation between air pressure and boiling point is directly proportional when air pressure increase, boiling point also increases on other hand when thepressure, decreases, boiling point of substance decreases.
As the mountains are concerned, the air pressure at the mountains is low due to height. That is why takes long time to cook at mountains.
Why milk is considered as an ideal food?
Milk is considered as an ideal food due to following reasons
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It contains all constitute of balanced diet.
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Milk contains fat.
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Milk has high nutritional value because it contains proteins as well as minerals.
Why the colour of sky is blue?
The colour of the sky is blue due to following reason.
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There are minute dust particles and water vapour in the atmosphere which scatter blue colour at higher altitudes.
