Question

Two satellites are moving around the earth in circular orbits at height R and 3R respectively, R being the radius of the earth, the ratio of their kinetic energies is

• A. 2
• B. 4
• C. 8
• D. 16

Answer 1

Answer: (A)

2

Answer 2

$r _ { 1 } = R + h _ { 1 } = R + R = 2 R$ and

$r _ { 2 } = R + h _ { 2 } = R + 3 R = 4 R$

Kinetic energy $\frac { ( K E ) _ { 1 } } { ( K E ) _ { 2 } } = \frac { r _ { 2 } } { r _ { 1 } } = \frac { 4 R } { 2 R } = \frac { 2 } { 1 }$.