Physics in Depth

NEB Grade XII 2079 (2022) Physics Question Solution New Course Group 'A' Rewrite the correct options of each question in your answer sheet. If L represents momentum, I represents moment of inertia, then \(\frac{L^2}{2I}\) represents Rotational kinetic energy Torque Power Potential energy Solution: Option (a) Explanation: Since, the rotational kinetic energy is commonly expressed as, \[\text{K.E.}=\frac{1}{2}mv^2\] Also, \[L=I\omega\] Then, \[\begin{align*} \text{K.E.}&=\frac{1}{2} I \times \frac{L^2}{I^2}\\ &=\frac{L^2}{2I}\\ \end{align*}\] Starting from mean position, a particle in simple harmonic motion takes time \(T_1\) and \(T_2\) to cover first half and next half displacement in moving from mean to extreme position, then