1.

An aeroplane fles a straight path from town (A) to townB, 500 km way . Town (B) is due East ot town (A) and a strong with blows from South to North at 1 300 km//h. Tf the lanes air speed is900 km//h. Which of following statements is true ?

Answer»

Trip time is ` 5 /6 sqrt 5 ) hour`
Plane's ground speed in ` 600 km//h`
Plane's heading is 30 degree SOUTH EAST.
plane' s heading is 60 degree south East.

Solution :Refer to Fig. 2 (CF). 50.AB = 500 km.
.
VELOCITY of WIND , ` v_w = 300 km//h` along ` AC`. The air plane can fly a st. path `AB` if the resultant velocity of aeroplane and with acts along ` AB`. It will be so it the velocity of aeroplane is represented by ` AD`.
V elocity along ` AB, ` v= sqrt (v_a^2 -v_w^2)`
` = sqrt ( 900^2 - 300 ^2 ) = sqrt ( 7200 ) = 600 sqr 2 km//h`
Time taken to reach ` B, t= S/v = ( 500 km )/(600 sqrt 2 km/h)`
` 5/( 6 sqrt 2)`
` sin theta = v_w /v_a = (300)/( 900) = 1/3 = 0 3333 = sin 19^2 28'`
` theta= 19^@ 28'`
` theta 19^@ 28' Suoth of East .


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