A rocket gains velocity because it loses mass.Where does Einstein Mass gain with velocity equation fit in?

Answer 1

Rockets are more dependent on Newton's law that "every action has an equal and opposite reaction" then on the fact that the rocket loses mass. Rockets are simply devices that shoot gas and energy out of a funnel to get an equal reaction that moves the craft. As the rocket burns fuel, it will lose weight, and that will allow it to accelerate faster with the same amount of thrust. A rocket would have to be moving very fast for Einstein's equations to play a noticeable part. Such a rocket is called a 'relativistic rocket', and is beyond our current technology.

Answer 2

A rocket does not gain velocity because it looses mass, it gains velocity because of the exhaust velocity. Rocket thrust is exactly like gun recoil that way. The gun does not kick because it looses the mass of the bullet, it kicks because of the muzzle velocity. The kick depends on both the mass of the bullet and the muzzle velocity, A bullet that just falls out of the gun produces no recoil no matter how heavy it is, but a small bullet can produce a big recoil if the muzzle velocity is really high. Similarly, rocket engines produce more thrust with less loss of mass (fuel burned) if the exhaust velocity is high. As has been stated in other answers above, it is Newton's third law, every action has an equal and opposite reaction. The action is the bullet being fired at high speed or the exhaust gasses leaving the rocket nozzle at high speed and the reaction is the gun kicking back the other way or the rocket being propelled forward.

Answer 3

At the speeds of rockets today, the mass change with velocity, due to relativity effects, is insignificant.

The formula is:
relativistic mass = (rest mass) * (1 - v^2 / c^2 ) ^ (-1/2)

At 30 km/sec, the ratio (relativistic mass) / (rest mass) is about
1.0000000050. A million kilogram rocket would gain 5 grams.

Answer 4

It kicks in about .9 times the speed of light.