Maths-
General
Easy
Question
A man travelling east at 8km/h finds that the wind seems to blow directly from the north. On doubling the speed, he finds that it appears to come from the north-east. The velocity of the wind is
The correct answer is:
The velocity of wind relative to man = Actual velocity of wind-Actual velocity of man
Let 
represent unit vectors along east and north. Let the actual velocity of wind be given by
In the first case the man’s velocity is 8i and that of the wind blowing from the north relative to the man is
Therefore
Comparing coefficients x-8=0 , y=-p In the second case when the man doubles his speed, it seems to come from the north -east
Hence, the velocity of wind is
Its magnitude is
Hence , its direction is from the north -west
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chemistry-General
