Question

A particle is moving eastwards with a velocity of $5\, m / s$. In $10\, s$ the velocity changes to $5\, m / s$ northwards. The average acceleration in this time is

• A. zero
• B. $\frac{1}{\sqrt 2} m/s^2$ towards north-east
• C. $\frac{1}{\sqrt 2} m/s^2$ towards north-west
• D. $\frac{1}{2} m/s^2$ towards north

Answer 1

Answer: (C)

$\frac{1}{\sqrt 2} m/s^2$ towards north-west

Answer 2

$a_av = \frac{\Deltav}{\Deltat}=\frac{v_f-v_i}{\Deltat}$
$\Delta v = 5 \sqrt 2 m/s$ in north-west direction.
$a_av = \frac{5 \sqrt 2}{10}=\frac{1}{\sqrt 2} m/s^2$ (in north-west direction)
$\therefore$ Correct option is (c).