Kinematics Question 520
Question: A bird it’s flying towards north with a velocity $ 40km{{h}^{-1}} $ and a train is moving with velocity $ 40km{{h}^{-1}} $ towards east. What is the velocity of the bird noted by a man in the train?
Options:
A)$ 40\sqrt{2}km{{h}^{-1}}N-E $
B)$ 40\sqrt{2}km{{h}^{-1}}S-E $
C)$ 40\sqrt{2}km{{h}^{-1}}N-W $
D)$ 40\sqrt{2}km{{h}^{-1}}S-W $
Show Answer
Answer:
Correct Answer: C
Solution:
[c] 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 the bird possesses two velocities,
$ \vec{v} $ B towards north and $ -{{\overrightarrow{v}} _{T}} $ along west.
$ | \vec{v}BT |=\sqrt{{{| \vec{v}B |}^{2}}+{{| -\vec{v}T |}^{2}}} $
[By formula, $ \theta =90{}^\circ $ ] $ =\sqrt{40^{2}+40^{2}}=40\sqrt{2} $
$ km{{h}^{-1}} $ north-west
