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7.Gravitation
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Let escape velocity of a body kept at surface of a planet is $u$. If it is projected at a speed of $200 \%$ more than the escape speed, then its speed in interstellar space will be ...........
A
$u$
B
$\sqrt{3} u$
C
$2 u$
D
$2 \sqrt{2} u$
Solution
(d)
Given:- Escape velocity $=u$
The initial velocity of projective is $200 \%$ more than the escape velocity
$\Rightarrow V_{\text {initial }}=u+2 u=3 u$
To find:- The speed of partich in interstellar space
$\Rightarrow$ when gravitational. potential evergy is $0$
Applying Law of Cousavation of energy:,
$\frac{1}{2} m V_{\text {initial }}^2+(P \cdot E)_{\text {initial }}=\frac{1}{2} m V_{\text {final }}^2+0$
$\therefore$ Velocity of the body in the intestella space $=2 \sqrt{2} 4$
Standard 11
Physics
