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7.Gravitation
medium
At what height over the earth's pole, the free fall acceleration decreases by one percent ........ $km$. (assume the radius of earth to be $6400 \,km$)
A
$32$
B
$80$
C
$1.253$
D
$64$
Solution
(a) $g \propto \frac{{GM}}{{{r^2}}}$ $⇒$ $g \propto \frac{1}{{{r^2}}}$or $r \propto \frac{1}{{\sqrt g }}$
If $g$ decrease by one percent then $r$ should be increase by $\frac{1}{2}\% $
i.e. $R = \frac{1}{{2 \times 100}} \times 6400 = 32\;km$
Standard 11
Physics
