A body is moving towards north with initial velocity of 13m/s. Its is subjected to a retardation of 2 m/s2 towards south.The distance travelled in 7th sec is ??

Joshi sir comment

displacement of any particular sec. = u+at-(a/2)

here direction of motion is opposite to the direction of acceleration so formula will be u-at+(a/2)

displacement in 7th sec = 0

now we know that direction of motion will become south after 6.5 sec. so distance for last half sec = ut+(1/2)at= 1/4

same will be the distance for the first half sec of 7th. so total distance for 7th sec = 1/4 + 1/4 = 1/2