Question

A helicopter of mass $1000kg$ rises with a vertical acceleration of $15m/s^2$. The crew and the passengers weigh $300kg$. Give the magnitude and direction of the
"force on the helicopter due to the surrounding air."

Answer 1

Step 3: Draw free body diagram of helicopter with passengers and crew.

Step 4: Find action on the rotor.

Let action of the air on the rotor is $F$, then using Newton’s second law of motion.

$F-mg=ma$
$F=m(g+a)$
$=1300(10+15)$
$=32500N$

So, force on the helicopter due to the surrounding air is $32500N$, in upward direction.

And using newton’s third law of motion, the action of the rotor on the surrounding air will be $=32500N$ acting downwards