First slide

Relative motion in 2 dimension

Question

A bird is flying towards north with a 40 ${kmh}^{- 1}$ and a train is moving with velocity 40 ${kmh}^{- 1}$ towards east. What is the velocity of the bird noted by a man in the train?

Moderate

A

$40 \sqrt{2} {kmh}^{- 1} N - E$
B

$40 \sqrt{2} {kmh}^{- 1} S - E$
C

$40 \sqrt{2} {kmh}^{- 1} N - W$
D

$40 \sqrt{2} {kmh}^{- 1} S - W$

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 the bird possesses two velocities, ${\vec{v}}_{B}$ towards north and $- {\vec{v}}_{T}$ along west.
$\begin{array}{l} |{\vec{v}}_{B T}| = \sqrt{{|{\vec{v}}_{B}|}^{2} + {|- {\vec{v}}_{T}|}^{2}} [By formula, θ = 90^{\circ}] \\ = \sqrt{40^{2} + 40^{2}} = 40 \sqrt{2} {kmh}^{- 1} north-west \end{array}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App