Question

A rocket is fired upward from the earth's surface such that it creates an acceleration of $19.6m{s}^{-2}$. If after $5s$, its engine is switched off, the maximum height of the rocket from earth's surface would be

• A. $980m$
• B. $735m$
• C. $490m$
• D. $245m$

Answer 1

The correct option is B $735m$

concept are attached, rest calculation is:
Velocity when the engine is switched off
$v=19.6\ast 5=9.8m/s$
$h_{max}=h_1+h_2$
where, $h_1=\frac{1}{2}a{t}^2\&h_2=\frac{v^2}{2a}$

$h_{max}=\frac{1}{2}\ast 19.6\ast 5\ast 5+\frac{98\ast 98}{2\ast 9.8}$

$=245+490=735m$

$B$ is correct answer