Why does a fan make noise while running on an invertor and not on normal electric supply?

Abdul Khabir, Jammu & Kashmir

Why and how do milk and water get separated when lime (juice) is added?

Lena saravanan, Tiruchengode, Tamil Nadu

How does a tall coconut tree stand erect in soft sand (at the seaside, for example) when it has no deep and complex root system? Some times a tree of height 15 metres or more stands at a precarious angle of 45 degrees or less in soft sand on the seaside.

K.S. Nair, Thiruvananthapuram