As mentioned, after the hovering period at 100 m

, the vehicle made a vertical powered
descent to h = 30 m, ending with a downward (!) velocity of 2 m/s at this altitude. Assume that the
engine provided a constant (!) thrust-to-weight ratio during this phase and that the gravitational
acceleration near the lunar surface is constant. How long lasted this phase of the descent?
a.
1.23 sec O
b.
9.26 sec O
c.
11.07 sec O
d.
70.00 sec O

Also given is:
Gravitational constant on the moon: 4.9028 x 10^3 km^3/s^2
Radius Moon: 1738 km

I can't seem to figure out how to solve this problem, any tips or help?

Using the standard SUVAT equations, one can calculate the average acceleration required to increase the vehicle's speed from 0 to 2 m/s using v^2 = u^2 + 2*a*s where you know u = 0 m/s and you want to solve for a. You'll discover a = 1/35 m/s^2. Using v = u + a*t, you find that t=70s which is indeed the answer to the question. The answer is simple only it is not clearly recognizable from the question.