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

Options

A. zero
B. `1/sqrt2 ms^(-2)` s towards north-west
C. `1/sqrt2 ms^(-2)` towards north-east
D. `1/sqrt2 ms^(-2)` towards north

Answer

B

Explanation

Velocity in eastward direction `= 5 hat i`
Velocity in northward direction `= 5 hatj`

`:.` Average acceleration `veca=(5hatj-5hati)/10=1/2hatj-1/2hati`
or `|veca|= sqrt((1/2)^2+(-1/2)^2)=1/sqrt2ms^(-2)` towards north - west