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Question: Answered & Verified by Expert
Assertion : Kepler's second law can be understood by conservation of angular momentum principle.
Reason : Kepler's second law is related with areal velocity which can further be proved to be based on conservation of angular momentum as $(d A / d t)=\left(r^2 \omega\right) / 2$.
PhysicsGravitationAIIMSAIIMS 2017
Options:
  • A If both assertion and reason are true and reason is the correct explanation of assertion.
  • B If both assertion and reason are true but reason is not the correct explanation of assertion.
  • C If assertion is true but reason is false.
  • D If both assertion and reason are false.
Solution:
2121 Upvotes Verified Answer
The correct answer is: If both assertion and reason are true and reason is the correct explanation of assertion.
According to Kepler's law, $\frac{d A}{d t}=$ constant As, $\frac{d A}{d t}=\frac{1}{2} r^2 \frac{d \theta}{d t}=\frac{1}{2} r^2 \omega$
$\begin{aligned} & \therefore \frac{m r^2 \omega}{2 m}=\frac{L}{2 m}=\text { constant } \\ & \therefore L=\text { constant }\end{aligned}$

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