A 05-Kg Model Helicopter Initially at Rest on the Ground,starts to to Move

Multiple Choice

A 0.5-kg model helicopter initially at rest on the ground,starts to move directly up under the effect of a lift force of magnitude of 7.4 N.After 12 seconds the engine stops and the helicopter starts free fall.Ignoring air resistance,calculate the helicopter's velocity just before hitting the ground.

A) -36.7 m/s
B) -48.4 m/s
C) -65.5 m/s
D) -103 m/s
E) -116 m/s