· The launching of Earth satellites should be from a place near the equator to take the fullest advantage of the earth’s movements. The regions of the Earth closer to the equator.
· The person jumping out of a moving train is carried forward in the direction of the train because the person himself is in motion sharing the velocity of the train and will continue in its state of uniform motion unless it exercises some force to prevent it (Newton’s first law of motion).
· The sky appears blue because the light of the sun is spread or scattered by the dust particles in the air. In space the sky would appear black as there are no dust or air particles to scatter the light.
· Ultrasonic waves are used for stirring liquid solutions because they can produce perfectly homogeneous solutions.
· Water extinguishes fire because as it evaporates, the temperature of the burning body is lowered, thus retarding or stopping the burning action also the resulting vapours surround the burning substance cutting off the oxygen supply thus inhibiting the burning process. In fact hot water will extinguish fire more quickly than cold water as hot water will vaporize faster.
· Water from a hand pump is warm in winter and cold in summer because in winter outside temperature is low and in summer outside temperature is higher as compared to the temperature of water obtained from underground which remains practically unchanged due to earth being bad conductor of heat.
· Water kept in an earthen pitcher becomes cold because the pitcher has minute pores on its surface which absorb water. Water in the pores evaporates when it comes in contact with air, and produces a cooling effect.
· We experience difficulty in breathing on mountains because the pressure of the air out side is less as compared to the pressure of the pressure of air inside the lungs.
· When a bottle of perfume is opened in one corner of a room the smell spreads soon throughout the room. This is an example of Diffusion.
· When a gun is fired at a visible distance, the sound is herd a little after the smoke is seen because the velocity of light is much higher than that of sound.
· When ice floating in a glass of water melts, the level of water remains unchanged because as a solid, ice displace an equal volume of water.
· Whenever there is water loss from the body, secretion of saliva is reduced resulting in dryness of the mouth and stimulating the sensation of thirst. Intake of fluid then helps in restoring the loss of the water.