If one of the four engines suddenly fail, so this means
that we only get 3 / 4 of the original force. Since force is the product of
mass and acceleration and mass is constant, therefore we get 3 / 4 of the
original acceleration.
So the remaining acceleration is:
a = (2.0 m/s^2) * (3 / 4)
a = 1.5 m/s^2
