Curious Facts

Question. Why is the thread attached to a kite curved at the top end?
A kite obtains lift to rise up in air when it deflects winds in the downward direction. When it is windy, the thread is held taut by the kite because it is being forced to rise up further in air. But when it is not windy and the kite is standing still in air, the weight of the thread comes into effect. It sags following a curved path.

Question. Why is the wheel of a motorcycle spoken while that of a scooter is not?
There is nothing sacrosanct about one wheel being spoked and another not. Motorcycle wheels have a large diameter and if one has to make these solid, they would become very heavy, leading to a large drag on the engine. Scooter wheels on the other hand have a smaller diameter and hence the wheel can be solid without too much increase in weight. In addition, a spoked wheel is difficult to maintain for it tends to get deshaped rather easily as compared to a solid wheel. So, where compromise for weight is possible a solid wheel is preferred. Now, with use of new materials like carbon fibre composites very light weight. Large diameter spoke-less wheels are being manufactured especially for racing bikes.

Question. Why do some people have blue eyes while others have brown or black eyes?
The colour of the eyes in human beings is due to the presence of a pigmented layer of cells in the muscular screen, the iris, which is located just behind the transparent cornea. It allows only the right amount of the light needed to produce a sharp and clear image. When the pigment, the melanin, is absent, the iris, though transparent looks blue because the light passing through the fluid – the adequous humour, behind it gets scattered, producing an effect similar to the one making the sky look blue. If the concentration of melanin is more, it looks brownish and with more pigments becomes darker. The spread of pigments in this layer is a hereditary character. In some the pigments may be sparser giving a blue colour to the eye. In others it could be denser and so the eye looks brown or black. Sometimes the blue eyes in a baby can turn brown when it grows up. This happens because the iris cells accumulate more pigments as the boy grows up.