Question:

Two planets A and B are orbiting around the sun. The distances of the two planets A and B from the sun are \(r_A\) and \(r_B\) respectively. Also \(r_B = 225\,r_A\). If the orbital speed of the planet A is 'V' then the orbital speed of planet B will be

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Orbital speed around the sun is inversely proportional to the square root of the orbit radius.
Updated On: Oct 1, 2026
  • \(\frac{V}{3}\)
  • \(\frac{V}{5}\)
  • \(\frac{V}{15}\)
  • \(\sqrt{15}\,V\)
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The Correct Option is C

Solution and Explanation

Step 1: Understanding the Concept:
For a planet in a circular orbit, gravity supplies the centripetal force: \(\frac{GMm}{r^2} = \frac{mv^2}{r}\), so \(v = \sqrt{\frac{GM}{r}}\).

Step 2: Ratio:
\[ \frac{v_A}{v_B} = \sqrt{\frac{r_B}{r_A}} = \sqrt{100} = 10 \]
The planet closer to the sun moves faster, which is consistent with the ratio being greater than 1.

Final Answer:
The ratio of the speeds is 10, option (C). \[ \boxed{10} \]
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