Question

how to find the thrust , kinematics

Answer 1

To give initial acceleration 20 m/s^2 Force required is
F = ma
= 5000kg × 20m/s^2
= 10^5 N

F = vdm/dt
dm/dt = F/v
= 10^5 / 800
= 125 kg/s

The amount of gas ejected per second to supply needed thrust is 125 kg/s
(c) is the correct option.