$A$ lead shot of $1\, mm$ diameter falls through a long column of glycerine. The variation of its velocity $v$ with distance covered is represented by

If $\int \frac{7x^8+8x^7}{(1+x+x^8)^2} dx = f(x) + c$,then $f(x)$ is equal to

Which of the following statements is not correct when a junction diode is in forward bias?

Which of the following is a polyamide?

........ of a reaction cannot be determined experimentally.

$A$ convex lens $A$ of focal length $20 \ cm$ and a concave lens $B$ of focal length $5 \ cm$ are kept along the same axis with a distance $d$ between them. If a parallel beam of light falling on $A$ leaves $B$ as a parallel beam,then the distance $d$ in $cm$ will be