Question

A helicopter of mass 2000 kg rises with a vertical acceleration of 15 m/s². The total mass of the crew and passengers is 500 kg. Give the magnitude and direction of the : 

(i) Force on the floor of the helicopter by the crew and passenger. 

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

(iii) Force on the helicopter due to the surrounding air (g =10 m/s²)

Answer 1

(a) Force on the floor of the helicopter by the crew and passengers = apparent weight of crew and passengers 

= 500 (10 + 15) 

= 12500 N

(b) Action of rotor of helicopter on surrounding air is Obviously vertically downwards, because helicopter rises on account of reaction of this force. Thus force of action 

= (2000 + 500) (10 + 15) 

= 2500 × 25 

= 62,500 N

(c) Force on the helicopter due to surrounding air is obviously a reaction. As action and reaction are equal and opposite, therefore 

Force of reaction F´ = 62,500 vertically upwards.