Question

A body is moving with velocity 30m/s towards east. after 10 seconds its velocity becomes 40m/s towards north. the average acceleration of the body is

Answer 1

use triangle law for resultant i.e root over 30^2 +40^2 = 50 then a = v/t i.e 50/10 = 5 m/s^2

Answer 2

Initial velocity = The velocity in east direction = 30i , where i is unit vector along x axis.

Final velocity = The velocity in north direction = 40j , where j is unit vector along y axis.

Average acceleration = { (root over(302+402))/10} m/s2

= 5 m/s2 in north east direction!