The ship that will speed up faster if they fire their rockets at the same time is; The one with the lower mass
We are told that;
There are two spaceships
Each spaceship has different masses
Each spaceship has rocket engines of identical force.
We know that formula for force is;
F = ma
Thus, if force is constant, the higher the mass, the lesser the acceleration and also the lesser the speed. Thus, the lower the mass the faster the speed.
This means the spaceship that will speed up faster will be the one with lesser mass.
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