In the given figure, let us take the position of mass when the spring is unstreched as x=0, and the direction from left to right as the positive direction of x-axis. Give x as a function of time t for the oscillating mass if at the moment we start the stopwatch (t =0), the mass is
(a) at the mean position,
(b) at the maximum stretched position.
In the given figure, let us take the position of mass when the spring is unstreched as x=0, and the direction from left to right as the positive direction of x-axis. Give x as a function of time t for the oscillating mass if at the moment we start the stopwatch (t =0), the mass is
(a) at the mean position,
(b) at the maximum stretched position.

Solution:

Distance travelled by the mass sideways is given as a=2.0 \mathrm{~cm}

Angular frequency of oscillation can be calculated as,

\omega=\sqrt{k} / \mathrm{m}

=\sqrt{1200 / 3}

=\sqrt{400}

=20 \mathrm{rad} \mathrm{s}^{-1}

(a) As time is noted from the mean position,

So, using

x=a \sin \omega t

We have,

x=2 \sin 20 t

(b) At maximum stretched position, the body is at the extreme right position, with an initial phase of \pi /2 rad. Then,

x=a \sin (\omega t+m / 2)

=\mathrm{a} \cos \omega \mathrm{t}

=2 \cos 20 \mathrm{t}