Question

An earth satellite S has an orbit radius which is 4 times that of a communication satellite C. The period of revolution of S is

• A. 4 days
• B. 8 days
• C. 16 days
• D. 32 days

Answer 1

Answer: (B)

8 days

Answer 2

Orbital radius of satellite $r _ { s } = 4 r _ { c }$ (given)

From Kepler’s law $T \propto r ^ { 3 / 2 }$ ∴ $\frac { T _ { s } } { T _ { c } } = \left( \frac { r _ { s } } { s _ { c } } \right) ^ { 3 / 2 } = ( 4 ) ^ { 3 / 2 }$

⇒ $T _ { s } = 8 T _ { c }$ $= 8 \times 1$ day = 8 days.