Carbohydrates,the most abundant biomolecules on Earth,are produced by:

During which phase of mitosis do the nuclear envelope and nucleolus completely disappear?

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

The formation of the oxide ion $O^{2-}_{(g)}$ requires first an exothermic and then an endothermic step as shown below:
$O_{(g)} + e^- \rightarrow O^{-}_{(g)}$; $\Delta H_{eg} = -142 \ kJ \ mol^{-1}$
$O^{-}_{(g)} + e^- \rightarrow O^{2-}_{(g)}$; $\Delta H_{eg} = +844 \ kJ \ mol^{-1}$
This is because:

An electromagnetic wave of intensity $1400 ~W/m^2$ falls on a metal surface of area $1.5 ~m^2$ and is completely absorbed by it. Find the force exerted by the beam.

How many double circulations are normally completed by the human heart in one minute?