In polymeric $(BeCl_2)_n$,there are

If the ratio of diameters,lengths and Young's moduli of steel and brass wires shown in the figure are $p, q$ and $r$ respectively,then the corresponding ratio of increase in their lengths would be

When $MnO_2$ is fused with $KOH$ in the presence of air,a coloured compound is formed. Identify the product and its colour.

Choose the incorrect pair for the characters given by Mendel regarding dominance and recessiveness.

The major product of the following reaction is

Two particles $A$ and $B$ initially at rest move towards each other under a mutual force of attraction. At the instant when the speed of $A$ is $v$ and the speed of $B$ is $2v$,the speed of the centre of mass of the system is