MCQ
A weight hangs by a spring $\&$ is caused to vibrate by a sinusoidal force .
Its displacement s$(t)$ at time $t$ is given by an equation of the form, $s(t) =$ $\frac{A}{{{c^2}\, - \,\,{k^2}}}$ $(sin\, kt - sin \,ct) $
where $A, c \& k $ are positive constants with $c \ne k,$ then the limiting value of the displacement as $c \to k$ is
- A$\frac{{ - \,At\,\,\,\sin \,kt}}{{2k}}$
- B$\frac{{ \,At\,\,\,\sin \,kt}}{{2k}}$
- C$\frac{{ \,At\,\,\,\cos \,kt}}{{2k}}$
- ✓$\frac{{ - \,At\,\,\,\cos \,kt}}{{2k}}$