Elbow joint is an example of

Statement $A$: Helium and Beryllium have the same outer electronic configuration of the type $ns^2$.
Reason $R$: Both are chemically inert.

With what minimum velocity should a block of mass $m$ be projected from the left end $A$ towards end $B$ such that it reaches the other end $B$ of a conveyor belt of length $L$ moving with a constant velocity $v$ in the opposite direction? The friction coefficient between the block and the belt is $\mu$.

If $(2, -1, 3)$ is the foot of the perpendicular drawn from the origin to a plane, then the equation of that plane is

An ideal gas expands isothermally from a volume $V_1$ to $V_2$ and is then compressed to the original volume $V_1$ adiabatically. The initial pressure is $P_1$ and the final pressure is $P_3$. If the total work done is $W$,then:

Which of the following statements is not true for two genes that show $50 \%$ recombination frequency?