question_answer

An aeroplane flies 400 m due north and then 300 m due south and then flies 1200 m upwards, the net displacement is:

A) greater than 1200 m      

B) less than 1200 m

C) 1400 m                 

D) 1500 m

Correct Answer: A

Solution :

As give in question \[OA=400\,m\](due north) \[AB=300\,m\](due south) \[\therefore \]   \[OB=OA-AB\] \[=400-300=100\] Also \[BC=1200\,m\](upwards) In right triangle \[\Delta OBC,\] \[O{{C}^{2}}=O{{B}^{2}}+B{{C}^{2}}\] \[\therefore \]  Displacement \[OC=\sqrt{O{{B}^{2}}+B{{C}^{2}}}\]                               \[=\sqrt{{{(100)}^{2}}+{{(1200)}^{2}}}\]                          \[=\sqrt{10000+1440000}\]                          \[=\sqrt{1450000}\]                      \[=1204\,m>\,1200\,m\] Hence, net displacement is greater than 1200 m.