Amachine gun fires 25 g bullets at the rate of 600 bullets per minute with a speed of 200 m/s. calculate the force required to keep the gun in position.

The rate of bullets per minute = 6000 per minute
= 6000/6 per sec 
=10 bullets per sec
as we know
F=n * m * v
=10 . 200 . 25 .10^-3
= 2N

Gas will most likely  fill the container 

W= fd
where f is an applied force and d is the distance over which it is applied. when a parachuting skydiver is at constant velocity, he is experiencing "terminal velocity", the point at which his acceleration down is canceled out by air resistance. that means that the resisting force of the air is equal to his weight, but in the opposite direction. with this, we can solve for the work done by the force.
w = fd
w = (92.0)(9.81 m/s^2) (325)
w= 2.93 x 10^5 j
the value for work in this case is positive because it is pushing up on the skydiver, who has a downward force of gravity.
therefore the answer is 2.93 x 10^5 j