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7.Gravitation
easy
The mass of a spaceship is $1000\ kg$. It is to be launched from the earth's surface out into free space. The value of $g$ and $R$( radius of earth) are $10\ m/s^2 $ and $6400\ km$ respectively. The required energy for this work will be
A
$6.4 \times 10^{10}$ $joules$
B
$6.4 \times 10^{11}$ $joules$
C
$6.4 \times 10^8 $ $joules$
D
$6.4 \times 10^9$ $ joules$
(AIEEE-2012)
Solution
The required energy for this work is given by
$\frac{{GMm}}{R} = mgR$
$ = 1000 \times 10 \times 6400 \times {10^3}$
$ = 6.4 \times {10^{10}}\,Joules$
Standard 11
Physics
