JEE PHYSICS MCQ: THERMAL PROPERTIES OF MATTER

A simple seconds pendulum is constructed out of a very thin string of thermal coefficient of linear expansion $\alpha=20 \times 10^{-4} /{ }^{\circ} \mathrm{C}$ and a heavy particle attached to one end. The free end of the string is suspended from the ceiling of an elevator at rest. The pendulum keeps correct time at $0^{\circ} \mathrm{C}$. When the temperature rises to $50^{\circ} \mathrm{C}$, the elevator operator of mass $60 \mathrm{~kg}$ being a student of Physics accelerates the elevator vertically, to have the pendulum correct time. Find the apparent weight of the operator when the pendulum keeps correct time at $50^{\circ} \mathrm{C}$. (Take $g=10 \mathrm{~m} / \mathrm{s}^2$ )