Which of the following oxides is the anhydride of orthophosphoric acid $(H_3PO_4)$?

The velocity $v$ reached by a car of mass $m$ at a certain distance from the starting point,driven with constant power $P$,is such that:

$(p \to q) \leftrightarrow (q \vee \sim p)$ is

The intensity of radiation emitted by the sun has its maximum value at a wavelength of $510 \ nm$ and that emitted by the north star has the maximum value at $350 \ nm$. If these stars behave like black bodies,then the ratio of the surface temperature of the sun and north star is

If the wavelength of an electromagnetic radiation is $2000 \ \mathring{A}$,what is its energy in ergs?

$P, Q$ and $R$ are long parallel straight wires in air, carrying currents as shown. The direction of the resultant force on $R$ is: