A satellite does not need any energy to revolve around the earth, why ?

A satellite rotates around the earth by using earth's gravitational force as centripetal force. Also as there is no air in space, it does not have to work against air resistance. Hence it doesn't lose any energy while rotating. So it does not require fuel to rotate around the earth.

firearm identification is the process of analyzing the bullets and cartridge cases left at a crime scene to determine if they came from a particular firearm. marks on the bullets and cartridges may be common to every firearm of that type. these are called class characteristics.