Q: A body starts from rest. what is the ratio of the distance traveled by the during the 4 ^{th} and 3 ^{th} seconds

(a) 7/5

(b) 5/7

(c) 7/3

(d) 3/7

Ans: (a)

Distance travelled in n^{th is}

$\large S_n = u + \frac{a}{2}(2n-1)$

$\large \frac{S_4}{S_3} = \frac{0 + \frac{a}{2}(2\times 4 -1)}{0 + \frac{a}{2}(2\times 3 -1)}$

= 7/5