Q 11-13-022NEETJEE MainMedium
A $1$ kg block on a spring of force constant $100$ N/m oscillates with frequency $f$. What mass must be added so that the frequency becomes $\dfrac{f}{2}$?
Answer: (D) $3$ kg
$f \propto \dfrac{1}{\sqrt{m}}$. Halving $f$ needs $4$ times the mass, i.e. $4$ kg in total, so $3$ kg must be added.
Solution by Sreeraj P, M.Sc Physics