If $x_1, x_2, \ldots, x_n$ are $n$ observations such that $\sum_{i=1}^n x_i^2 = 400$ and $\sum_{i=1}^n x_i = 80$,then the least value of $n$ is

Which of the following is the family of sunflower?

Which of the following representations correctly explains the function of a mitochondrion?

Two identical blocks $A$ and $B$,each of mass $m$,are placed on a smooth horizontal surface and are connected by a light spring of length $L$ and force constant $k$. $A$ third identical block $C$ of mass $m$ moves along the line joining $A$ and $B$ with velocity $v$ and collides with block $A$. The maximum compression in the spring is:

Match the following:
| Column $I$ | Column $II$ |
| :--- | :--- |
| $A$. Hooke's law | $1$. Tangential strain |
| $B$. Shearing strain | $2$. Temporary loss of elastic property |
| $C$. Bulk strain | $3$. Elastic limit |
| $D$. Elastic fatigue | $4$. $3$ times the linear strain |

$A$ parallel plate capacitor of capacity $C_0$ is charged to a potential $V_0$. $(i)$ The energy stored in the capacitor when the battery is disconnected and the plate separation is doubled is $E_1$. (ii) The energy stored in the capacitor when the charging battery is kept connected and the separation between the capacitor plates is doubled is $E_2$. Then,the value of $E_1 / E_2$ is: