A bird is flying towards north with a velocity 40km/h and a train is moving with a velocity 40km/h towards east. What is the velocity of the bird noted by a man in the train?

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$40 \sqrt{2} k m / h S - E$

$40 \sqrt{2} k m / h N - W$

$40 \sqrt{2} k m / h N - E$

$40 \sqrt{2} k m / h S - W$

answer is C.

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Detailed Solution

To find the relative velocity of bird w.r.t train, superimpose velocity

$- {\vec{V}}_{T}$ on both the objects. Now as a result of it, the train is at rest,

while bird posses two velocities $- {\vec{V}}_{B}$ towards N and $- {\vec{V}}_{T}$ along west.

Where, $- {\vec{V}}_{B}$ = Velocity of bird

$- {\vec{V}}_{T}$ = Velocity of train.

$| {\vec{V}}_{B T} | = \sqrt{| {\vec{V}}_{B} |^{2} + | {\vec{- V}}_{T} |^{2}}$

[By formula, $∴ θ = 90^{0}$ ]

$= \sqrt{40^{2} + 40^{2}} = 40 \sqrt{2} k m / h r N o r t h - W e s t$

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