A helicopter of mass 2000 kg rises with a vertical acceleration of 15 m s^-2. The total mass of the crew and passengers is 500 kg. Choose the correct statements from the following. (Take g = 10 m s^-2)

1. The force on the floor of the helicopter by the crew and passengers is $1.25\times {10}^4 N$ vertically downwards.
2. The action of the rotor of the helicopter on the surrounding air is 6.25 x 10⁴ N vertically downwards.
3. he force on the helicopter due to the surrounding air is $6.25\times {10}^4 N$ vertically upwards.

Here, Mass of helicopter, $M=2000 kg$

Mass of the crew and passengers, $m=500 kg$

Vertically upwards acceleration, $a=15 m s^{-2}, g=10 m s^{-2}$

(1) Force on the floor by the crew and passengers

 $$\begin{gathered} =m(g+a) \\ =500 kg(10+15) m s^{-2} \\ =12500 N \\ =1.25\times {10}^4 N \end{gathered}$$

It acts vertically downwards.

(2) Action of the rotor of the helicopter on the surrounding air

 $$\begin{gathered} =(M+m)(g+a) \\ =(2000+500) kg (10+15) m s^{-2} \\ =62500 N \\ =6.25\times {10}^4 N \end{gathered}$$

It acts vertically downwards.

(3 ) Force on the helicopter due to the surrounding air is equal and opposite to the action of the rotor of the helicopter on the surrounding air.

$\therefore$ Force on the helicopter due to the surrounding air $=6.25\times {10}^4 N$

It acts vertically upwards.