Why is Cooking Quicker in a Pressure Cooker?

Question : Why is cooking quicker in a pressure cooker?
Answer : As the pressure inside the cooker increases, the boiling point of water is raised, hence, the cooking process is quicker.

Question : Why does a man fall forward when he jumps out of a running train or bus?
Answer : He is in motion while on the train or bus. When he jumps out, his feet come to rest while touching the ground but his upper portion which is still in motion propels him forward.

Question : Why does an ordinary glass tumbler crack when very hot tea or milk is poured in it?
Answer : When a hot liquid is poured into a tumbler, the inner layer of the tumbler gets heated, it expands before the outer layer and an unequal expansion of both layers causes the tumbler to crack.

Question : Why is a compass used as an indicator of direction?
Answer : The magnetic needles of a compass under the influence of the earth’s magnetic field lie in a north-south direction. Hence, we can identify direction.

Question : Why is water from a hand pump warm in winter and cold in summer?
Answer : In winter the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.

Question : Why is a rainbow seen after a shower?
Answer : After a shower the clouds containing water droplets act like a prism through which the white light is dispersed producing a spectrum.

Question : Why does a swimming pool appear less deep than it actually is?
Answer : The rays of light coming from the bottom of the pool pass from a denser medium (water) to a rarer medium (air) and are refracted (bend away from the normal). When the rays return to the surface they form an image of the bottom of the pool at a point which is little above the real position.

Question : Why is one’s breath visible in winter but not in summer?
Answer : In winter, water vapor contained in the breath condenses into small droplets which become visible but in summer they are quickly evaporated and not seen.

Question : Why doesn’t the electric filament in an electric bulb burn up?
Answer : Firstly, because it is made of tungsten which has a very high melting point (341O°C) whereas the temperature of the filament required to glow is only 2700°C. Secondly, oxygen is absent since the bulb is filled with an inert gas which does not help in burning.

Question : Why does blotting paper absorb ink?
Answer : Blotting paper has fine pores which act like capillaries. When a portion of blotting paper is brought in contact with ink, ink enters the pores due to surface tension (capillary action of liquids) and is absorbed.

Question : Why does a small ball of iron sink in water but a large ship float?
Answer : The weight of water displaced by an iron ball is less than its own weight, whereas water displaced by the immersed portion of a ship is equal to its weight (Archimedes’ Principle).