What does the part labeled '$A$' in the given figure represent?

The velocities of two particles $A$ and $B$ are $0.05 \ ms^{-1}$ and $0.02 \ ms^{-1}$ respectively. The mass of $B$ is five times the mass of $A$. The ratio of their de-Broglie's wavelength is

If $I_n = \int_0^{\pi / 4} \tan^n x \, dx$, then $I_2+I_4, I_3+I_5, I_4+I_6, \ldots$ are in

The blocks shown in the figure move with a constant velocity of $10 \, m/s$ towards the right. All surfaces in contact are rough. The friction force applied by block $B$ on block $A$ is ........... $N$.

If the equation $x^2+2 \sqrt{2} xy+2y^2+4x+4 \sqrt{2}y+1=0$ represents a pair of parallel straight lines,find the distance between them.

What is the wavelength of light with a frequency of $100\; Hz$?