A particle moves towards east with velocit

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A particle moves towards east with velocity $5\, m/s$. After $10$ seconds its direction changes towards north with same velocity. The average acceleration of the particle is

A

Zero

B

$\frac{1}{{\sqrt 2 }}\,m/{s^2}\,N - W$

C

$\frac{1}{{\sqrt 2 }}\,m/{s^2}\,N - E$

D

$\frac{1}{{\sqrt 2 }}\,m/{s^2}\,S - W$
A particle moves towards east with velocity $5\, m/s$. After $10$ seconds its direction changes towards north with same velocity. The average acceleration of the particle is
$\Delta v = 2v\sin \left( {\frac{\theta }{2}} \right) = 2 \times 5 \times \sin 45^\circ $=$\frac{{10}}{{\sqrt 2 }}$
$⇒$  $a = \frac{{\Delta v}}{{\Delta t}} = \frac{{10/\sqrt 2 }}{{10}} = \frac{1}{{\sqrt 2 }}\;m/{s^2}$