Question:medium

Two satellites A and B go around a planet in circular orbits having radii of 4R and R, respectively. If the velocity of satellite A is 3v, the velocity of satellite B will be:

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Remember the relationships for orbital motion: - Velocity: \( v \propto 1/\sqrt{r} \) (closer satellite is faster) - Period: \( T \propto r^{3/2} \) (closer satellite has shorter period)
Updated On: Feb 18, 2026
  • 18v
  • 12v
  • 6v
  • 3v
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The Correct Option is C

Solution and Explanation

Step 1: Formula for orbital velocity.The velocity (\(v\)) of a satellite in a circular orbit (radius \(r\)), around a planet (mass \(M\)), is found by equating gravitational and centripetal forces:\[ \frac{GMm}{r^2} = \frac{mv^2}{r} $\Rightarrow$ v = \sqrt{\frac{GM}{r}} \]Orbital velocity is inversely proportional to the square root of the orbital radius: \( v \propto \frac{1}{\sqrt{r}} \).

Step 2: Ratio for satellites A and B.\[ \frac{v_B}{v_A} = \frac{\sqrt{GM/r_B}}{\sqrt{GM/r_A}} = \sqrt{\frac{r_A}{r_B}} \]

Step 3: Substitute values and solve for \(v_B\).- \( v_A = 3v \)- \( r_A = 4R \)- \( r_B = R \)\[ \frac{v_B}{3v} = \sqrt{\frac{4R}{R}} = \sqrt{4} = 2 \]\[ v_B = 2 \times (3v) = 6v \]

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