Q 11-13-044JEE MainJEE Main 2026 (28 Jan, Shift 2)Easy
As shown in the figure, a spring is kept in a stretched position with some extension by holding the masses $1$ kg and $0.2$ kg with a separation more than spring natural length and are released. Assuming the horizontal surface to be frictionless, the angular frequency (in SI unit) of the system is :
Answer: (C) 30
Two free masses joined by a spring oscillate with the reduced mass
$$\mu = \frac{m_1m_2}{m_1+m_2} = \frac{1\times0.2}{1.2} = \frac16\ \text{kg}$$
$$\omega = \sqrt{\frac k\mu} = \sqrt{150\times6} = 30\ \text{rad/s}$$
Solution by Sreeraj P, M.Sc Physics