The correct order of the $O-O$ bond length in $O_2$,$H_2O_2$ and $O_3$ is

Which tissue provides mechanical support to the young stem and petiole of leaves?

Extraction of zinc from zinc blende is achieved by

At a certain place,a magnet makes $30$ oscillations per minute. At another place where the magnetic field is double,its time period will be:

Two sources $A$ and $B$ are sending notes of frequency $680 \, Hz$. A listener moves from $A$ towards $B$ with a constant velocity $u$. If the speed of sound in air is $340 \, ms^{-1}$, what must be the value of $u$ so that the listener hears $10$ beats per second (in $ \, ms^{-1}$)?

An atomic power nuclear reactor can deliver $300\, MW$. The energy released due to fission of each nucleus of a uranium atom ${U^{238}}$ is $170\, MeV$. The number of uranium atoms fissioned per hour will be