Question

A body moving with some initial velocity and having uniform acceleration attains a final velocity $vm/s$ after travelling $xm$ . If its final velocity is $v=\sqrt{180-7x}$ , find the acceleration of the body.

• A. $-3.5m/s^2$
• B. $-7.5m/s^2$
• C. $-15m/s^2$
• D. $-30m/s^2$

Answer 1

Answer: (A)

$v=\sqrt{180-7x}$ where $x$ is the distance,
$\therefore v^2=180-7x$
From the dimensions, $180$ has dimensions of square of velocity.
For a body travelling with uniform acceleration,
$v^2-u^2=2aS$ is valid. By inspection one can say
$u^2=180$ , $2aS=-7x$ . (here $S=x)$
$-7x=2ax$ .
$\therefore a=-3.5m/s^2$