You have twice posted problems in which you said you were given replies that were nonsense. I am beginning to question your veracity, and certainly, your understanding of basic physics. What bothers me most it you seem to be presenting no analysis nor thinking, but fishing for answers.
See this:
http://www.jiskha.com/display.cgi?id=1190238213
A 4610 kg helicopter accelerated upwards at 2 m/s^2. What lift force is exerted by the air on the propellers?
I was given this reply:
The air force on the prop blades is what accelerates the helicopter upward.
Use good old Newton's second law:
F = M a
Concern: When I mulplied the mass of the helicopter (4610 kg) by the acceleration (2 m/s^2) the answer was incorrect. What am I doing wrong?
2 answers
It was I who posted the previous answer.
I should have clarified by saying that
NET force = (Blade force)-(Weight) = M a
Thus
Blade force = Weight + M a
= M (g + a)= (4610)(9.8 + 2)
I should have clarified by saying that
NET force = (Blade force)-(Weight) = M a
Thus
Blade force = Weight + M a
= M (g + a)= (4610)(9.8 + 2)
2 answers