Which of the following processes does not involve a catalyst?

Restriction enzymes were discovered by

How many bridging oxygen atoms are present in $P_4O_{10}$?

If the number average molecular weight and weight average molecular weight of a polymer are $40000$ and $60000$ respectively,the polydispersity index of the polymer will be

The length of an elastic string is $a$ metres when the longitudinal tension is $4 \ N$ and $b$ metres when the longitudinal tension is $5 \ N$. The length of the string in metres when the longitudinal tension is $9 \ N$ is

$A$ rocket of mass $M$ is launched vertically from the surface of the earth with an initial speed $V$. Assuming the radius of the earth to be $R$ and negligible air resistance,the maximum height attained by the rocket above the surface of the earth is