The partial pressure of oxygen in the alveoli of the lungs is

$A$ straight line $L$ at a distance of $4$ units from the origin makes positive intercepts on the coordinate axes,and the perpendicular drawn from the origin to this line makes an angle of $60^{\circ}$ with the line $x+y=0$. Then the equation of the line $L$ is

$A$ horizontal force of $10\, N$ is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is $0.2$. The weight of the block is ........ $N$.

Which one of the following is not a condensation polymer?

Soil erosion can be prevented by

$A$ metal rod of length '$l$' rotates about one of its ends in a plane perpendicular to a magnetic field of induction '$B$'. If the e.m.f. induced between the ends of the rod is '$e$',then the number of revolutions made by the rod per second is