A particle is moving eastwards with a velocity of 5 m/s in 10 seconds the velocity changes to 5 m/s northwards. The average acceleration in this time is
(1) 1/√2 m/s2 towards north-east
(2) 1/2 m/s2 towards north.
(3) zero
(4) 1/√2 m/s2 towards north-west