Why do we normally swing our hands while walking and why not when we carry a load in our hands?
- The center of gravity of a body depends on the distribution of mass in the body. When we walk, the movement of the legs tends to cause a shift in the center of the gravity of the body. To compensate this shift we swing our hands. When we are carrying a load in the hands, however, the effective center of gravity is lower, making it easier to maintain the balance.
How does a kingfisher catch fish?
- The kingfisher flies vertically over the position of the fish, then plunges into water at \(90^\circ\) angle. The notion here is that normal incident rays do not undergo refraction, hence the fish lies exactly where it appears to be. At any other angle than\(90^\circ\), the apparent location of the fish would be different from its real location.
Why does the salt become damp when kept exposed during the rainy season and not when exposed during summer season?
- In the rainy season humidity in the atmosphere is very high, then calcium chloride (CaCl) which is an impurity in the common salt, absorbs this moisture and makes the salt damp. In summer as the temperature is high, calcium chloride tends to loose moisture through the process of evaporation and the salt is left free-flowing.
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