Which element is used in pencil

What is the minimum distance required for an obstacle to produce a distinct echo?

What is the pH of Urine ?

The S.I. unit of the electric flux is

Heat stored in water vapour is –

Water gets cooled, when ice is immersed in it, this phenomenon is known as

What is the speed of light in air?

I threw a ball horizontally on the road and after covering certain distance, the ball stopped due to

A rear-view mirror for driving is –

Who defined the law of gravitation? 

Which law is also called the law of inertia?