Q: A body sliding down on a smooth inclined plane slides down 1/4 th distance in 2 sec. It will slide down the complete plane in

(a) 4 sec

(b) 2 sec

(c) 5 sec

(d) 3 sec

Ans:(a)

Sol: As u = 0, and a is constant

Applying $\displaystyle S = u t + \frac{1}{2}a t^2 $

In first case ,

$\displaystyle S/4 = 0 + \frac{1}{2}a 2^2 $ ..(i)

In second case ,

$ \displaystyle S = 0 + \frac{1}{2}a t^2 $ ..(ii)

Dividing (ii) by (i), we get

$ \displaystyle 4 = \frac{t^2}{4}$

t = 4 sec