Statement – I: For the planets orbiting around the sun, angular speed, linear speed and KE change with time, but angular momentum remains constant.
Statement – II: No torque is acting on the rotating planet. So its angular momentum remains constant.

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Statement – I is false, statement – II is true

Statement – I is true and statement – II is true, statement – II is the correct explanation for statement – I

Statement – I is true and statement – II is true, statement – II is not the correct explanation for statement – I

Statement – I is true, statement – II is false

answer is A.

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Detailed Solution

Net torque acting on the rotating planet is zero $i . e τ = 0$

Using $\frac{d L}{d t} = τ$

Thus $τ = 0 \Rightarrow L = c o n s \tan t$

Hence angular momentum is constant. So reason statement is correct.

Now $L = m v r = c o n s \tan t \Rightarrow v r = c o n s \tan t$

Thus as the distance between sun and planet changes, linear speed of the planet changes and this its kinetic energy also changes and thus its kinetic also changes. Also using $L = m r^{2} w = c o n s \tan t \Rightarrow r^{2} w = c o n s \tan t$

Thus as the distance between sun and planet changes, angular speed of the planet changes. Hence assertion statement is also correct and reason explains the assertion very well.

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