To solve this problem we will apply the concepts related to Newton's second law that relates force as the product between acceleration and mass. From there, we will get the acceleration. Finally, through the cinematic equations of motion we will find the time required by the object.
If the Force (F) is 42N on an object of mass (m) of 83000kg we have that the acceleration would be by Newton's second law.
Replacing,
The total speed change
we have that the value is 0.71m/s
If we know that acceleration is the change of speed in a fraction of time,
We have that,
Therefore the Rocket should be fired around to 1403.16s