JEE Mains · Physics · STD 11 - 6. system of particles and rotational motion
A fly wheel having mass 3 kg and radius 5 m is free to rotate about a horizontal axis. A string having negligible mass is wound around the wheel and the loose end of the string is connected to a 3 kg mass. The mass is kept at rest initially and released. Kinetic energy of the wheel when the mass descends by 3 m is ___________ J. (\(g=10~m/s^{2}\))
- A 30
- B 60
- C 45
- D 90
Answer & Solution
Correct Answer
(A) 30
Step-by-step Solution
Detailed explanation
\(mg\times3=\frac{1}{2}.\frac{mR^{2}}{2}\omega^{2}+\frac{1}{2}mv^{2}\) ...(i) & \(v=\omega R\) ...(ii) From equation (i) & (ii) \(g\times3=\frac{3}{4}.v^{2}\) K.E. of flywheel \(=\frac{1}{2}\times\frac{mR^{2}}{2}\times\omega^{2}=\frac{1}{4}mv^{2}\)…
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