JEE Mains · Physics · STD 11 - 6. system of particles and rotational motion
A person of \(80\, kg\) mass is standing on the rim of a circular platform of mass \(200\, kg\) rotating about its axis as \(5\) revolutions per minute \((rpm).\) The person now starts moving towards the centre of the platform. What will be the rotational speed (in \(rpm\) ) of the platform when the person reaches its centre \(......rpm\)
- A \(7\)
- B \(20\)
- C \(15\)
- D \(9\)
Answer & Solution
Correct Answer
(D) \(9\)
Step-by-step Solution
Detailed explanation
\(L _{ i }= L _{ f }\) \(\left(80 R ^{2}+\frac{200 R ^{2}}{2}\right) \omega=\left(0+\frac{200 R ^{2}}{2}\right) \omega_{1}\) \(180 \omega_{0}=100 \omega_{1}\) \(\omega_{1}=1.8 \omega_{0}=1.8 \times 5\) \(=9 rpm\)
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