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

Question

A rocket is fired upward from the earth's surface such that it creates an acceleration of 19.6 ms -2. If after 5 s, its engine is switched off, the maximum height of the rocket from earth's surface would be (A) 980 m (B) 735 m (C) 490 m (D) 245 m

Tardigrade Admin · Accepted Answer

Velocity when the engine is switched off v=19.6 × 5=98 ms -1 h max =h1+h2 text where h1=(1/2) a t2 h2=(v2/2 a) h max =(1/2) × 19.6 × 5 × 5+(98 × 98/2 × 9.8)=735 m

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

$980 m$

$735 m$

$490 m$

$245 m$

Velocity when the engine is switched off
$v = 19.6 \times 5 = 98 m s^{- 1}$
$h_{m a x} = h_{1} + h_{2} where h_{1} = \frac{1}{2} a t^{2} & h_{2} = \frac{v ^{2}}{2 a}$
$h_{m a x} = \frac{1}{2} \times 19.6 \times 5 \times 5 + \frac{98 \times 98}{2 \times 9.8} = 735 m$

Q. A rocket is fired upward from the earth's surface such that it creates an acceleration of 19.6ms−2. If after 5s, its engine is switched off, the maximum height of the rocket from earth's surface would be

980m

735m

490m

245m