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

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The Answer of 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

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