$A$ rocket with a lift-off mass $2 \times 10^4 \ kg$ is blasted upwards with an initial acceleration of $5 \ m \ s^{-2}$. The initial thrust of the blast is (Take $g = 10 \ m \ s^{-2}$)

The angle of a prism is $A.$ One of its refracting surfaces is silvered. Light rays falling at an angle of incidence $2A$ on the first surface return back through the same path after suffering reflection at the silvered surface. The refractive index $\mu$ of the prism is

The hydroxides and carbonates of sodium and potassium are easily soluble in water,while the corresponding salts of magnesium and calcium are sparingly soluble in water. Explain.

Which of the following is an amphoteric oxide?

If $\lim _{x \rightarrow \infty}\left(\frac{x^2+x+1}{x+1}-ax-b\right)=4$,then

The structure of $X$ is