A helicopter is moving to the right at a constant horizontal velocity. It experiences three forces \[{{\vec{F}}_{gravitational}},\] and force on it caused by rotor \[{{\vec{F}}_{rotor.}}\]Which of the following diagrams can be a correct free-body diagram representing forces on the helicopter? |
A)
B)
C)
D)
Correct Answer: C
Solution :
\[{{\vec{F}}_{gravitation}}\] acts downwards. \[{{\vec{F}}_{\operatorname{drag}}}\]act opposite to the direction of the motion. Now let us how \[{{\vec{F}}_{\operatorname{rotor}}}\]acts. | |
[a] | [b] |
Wings of the helicopter will push the air perpendicular to their plane of rotation as shown in Fig. [a]. From the third law, air will apply force \[{{\vec{F}}_{\operatorname{rotor}}}\]On the wings as shown in Fig. [b]. | |
There is no force\[ma\]. Basically, \[ma\]is the resultant of all the forces acting on a body. Moreover, here a is zero because velocity of the helicopter is constant. |
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