A helicopter of m ass 1000 kg rises with a vertical a c c ele ra tio n o f 15 ms-^(2) . The crew an d th e passengers weigh 300 kg. Give the magnitude and direction of the,(a) Force on th e floor by th e crew and passengers. (b) Action of the rotor of the helicopter on the surrounding air. (c) Force on the helicopter due to the surrounding air.

A helicopter of m ass 1000 kg rises with a vertical a c c ele ra tio n

1.	A helicopter of m ass 1000 kg rises with a vertical a c c ele ra tio n o f 15 ms-^(2) . The crew an d th e passengers weigh 300 kg. Give the magnitude and direction of the,(a) Force on th e floor by th e crew and passengers. (b) Action of the rotor of the helicopter on the surrounding air. (c) Force on the helicopter due to the surrounding air.
Answer» Solution :(a) ‘Free BODY’:crew and passengers Force on the system by the floor = F UPWARDS, weight of system = mg downwards, ` thereforeF – mg = ma` ` F- 300xx 10 = 300 xx 15` ` F= 7.5 xx 10^3 N ` upward By the Third Law, force on the floor by the crew and passengers = `7.5 xx 10^3 N`downwards. (B) ‘Free body’ :helicopter plus the crew and passengers Force by air on the system = R upwards, weight of system = mg downwards ` therefore R – mg = ma` `R - 1300 xx 10=1300 xx 15` ` R= 3.25 xx 10^4 N `upwards By the Third Law, force (action) on the air by the helicopter = `3.25 xx 10^4 N ` downwards. (c ) `3.25 xx 10^4 N ` upwards