If a body is moving in a circle of radius $r$ with a constant speed $v$,its angular velocity is

$A$ body of mass $200\,g$ is tied to a spring of spring constant $12.5\,N/m$,while the other end of the spring is fixed at point $O$. If the body moves about $O$ in a circular path on a smooth horizontal surface with a constant angular speed of $5\,rad/s$,then the ratio of the extension in the spring to its natural length will be:

$A$ uniform cube is subjected to volume compression. If each side is decreased by $1\%,$ then the bulk strain is

The solution of $(x^2+y^2) dx = 2xy dy$ is:

Two point charges $-q$ and $+q$ are located at points $(0, 0, -a)$ and $(0, 0, a)$ respectively. The electric potential at a point $(0, 0, z)$,where $z > a$ is

Gold numbers of protective colloids $A$,$B$,$C$ and $D$ are $0.50$,$0.01$,$0.10$ and $0.005$,respectively. The correct order of their protective powers is