First slide

Rectilinear Motion

Question

A particle moves in a straight line with a constant acceleration. It changes its velocity from $10 m / s t o 20 m / s$ while passing through a distance 135m in ‘t’sec . The value of ‘t’ is…………

Easy

A

1.8 s
B

9s
C

12s
D

10s

Solution

$\begin{array}{l} u = 10 m / s \\ v = 20 m / s \\ s = 135 m \end{array}$
From equation $v^{2} - u^{2} = 2 a s$
$\Rightarrow {(20)}^{2} - {(10)}^{2} = 2 a (135)$
$∴ a = \frac{400 - 100}{270} = \frac{30}{27} m / s^{2}$
Time taken is $t = \frac{v - u}{a}$
$= \frac{20 - 10}{(\frac{30}{27})} = \frac{270}{30}$
$= 9 s$

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