$ \Rightarrow 10g = k \times 0.25$
$\Rightarrow k = \frac{{10g}}{{0.25}} = 98 \times 4$
Now $T = 2\pi \sqrt {\frac{m}{k}}$
$\Rightarrow m = \frac{{{T^2}}}{{4{\pi ^2}}}k$
$ \Rightarrow m = \frac{{{\pi ^2}}}{{100}} \times \frac{1}{{4{\pi ^2}}} \times 98 \times 4 = 0.98\;kg$

$(a)$ Potential energy is always equal to its $K.E.$
$(b)$ Average potential and kinetic energy over any given time interval are always equal.
$(c)$ Sum of the kinetic and potential energy at any point of time is constant.
$(d)$ Average $K.E.$ in one time period is equal to average potential energy in one time period.
Choose the most appropriate option from the options given below:


| Column $I$ | Column $II$ |
| $(A)$ Potential energy of a simple pendulum (y axis) as a function of displacement ( $\mathrm{x}$ axis) | $Image$ |
| $(B)$ Displacement (y axis) as a function of time (x axis) for a one dimensional motion at zero or constant acceleration when the body is moving along the positive $\mathrm{x}$-direction | $Image$ |
| $(C)$ Range of a projectile (y axis) as a function of its velocity ( $\mathrm{x}$ axis) when projected at a fixed angle | $Image$ |
| $(D)$ The square of the time period (y axis) of a simple pendulum as a function of its length ( $\mathrm{x}$ axis) | $Image$ |

