Q: A particle moves in a straight line with a constant acceleration. It changes its velocity from 10 ms^{–1} to 20 ms^{–1} while passing through a distance 135 m in t sec. The value of t is

(a) 10

(b) 1.8

(c) 12

(d) 9

Ans: (d)

Sol:

Acceleration, a = (20-10)/t = 10/t

Using ,

$ \displaystyle v^2 = u^2 + 2 a s$

$\displaystyle 20^2 = 10^2 + 2 (10/t) \times 135 $