[ પૃથ્વીની ત્રિજ્યા $=6400\,km$, પૃથ્વીનું દળ $=6 \times 10^{24}\, kg$ ]
\(T _{ A }=2 \pi \sqrt{\frac{(6400+600) \times 10^{3}}{ GM }}\)
\(T _{ A }=2 \pi \times 10^{9} \sqrt{\frac{7^{3}}{ GM }}\)
\(T _{ B }=2 \pi \times 10^{9} \sqrt{\frac{8^{3}}{ GM }}\)
\(T _{ B }- T _{ A }=\frac{2 \pi 10^{9}}{\sqrt{ GM }}[8 \sqrt{8}-7 \sqrt{7}]\)
\(=314 \times 4.107\)
\(=1289.64\)
\(=1.289 \times 10^{3} s\)