The structure of $Cl_2O_7$ is ......

$A$ plank with a box on it at one end is gradually raised about the other end. As the angle of inclination with the horizontal reaches $30^o$,the box starts to slip and slides $4.0\, m$ down the plank in $4.0\, s$. The coefficients of static and kinetic friction between the box and the plank will be,respectively:

Pure $Si$ at $500\, K$ has equal number of electron $(n_e)$ and hole $(n_h)$ concentrations of $1.5 \times 10^{16} \,m^{-3}$. Doping by indium increases $n_h$ to $4.5 \times 10^{22} \,m^{-3}$. The doped semiconductor is of

The horizontal range is four times the maximum height attained by a projectile. The angle of projection is ......... $^o$

If $x$ is numerically so small that $x^2$ and higher powers of $x$ can be neglected,then $\left(1+\frac{2 x}{3}\right)^{3 / 2} \cdot(32+5 x)^{-1 / 5}$ is approximately equal to

On addition of $1 \, mL$ of $10 \% \, NaCl$ solution to $10 \, mL$ gold sol in the presence of $0.25 \, g$ of starch,the coagulation is just prevented. The gold number of starch is: