In the final stages of a moon landing, a lunar module descends under retro-thrust of its descent engine to a height of &

[answerhappygod]

In the final stages of a moon landing, a lunar module descends
under retro-thrust of its descent engine to a height of 𝑠 = 4 m
above the lunar surface where it has a downward velocity of 4 m/s.
Calculate the impact velocity with the moon’s surface if the
acceleration under the combined effect of gravity and retro-thrust
is the following function of height 𝑎 = 𝑠/2
Hint: Acceleration is not constant. The positive direction is
up.