The surface of the lake is at $2^{\circ}C$. Find the temperature of the bottom of the lake in $^{\circ}C$.

Let $P, Q, R$ and $S$ be the points on the plane with position vectors $-2 \hat{i}-\hat{j}$,$4 \hat{i}$,$3 \hat{i}+3 \hat{j}$ and $-3 \hat{i}+2 \hat{j}$ respectively. Then the quadrilateral $PQRS$ must be a

For all integers $n \geq 1$, which of the following is divisible by $9$?

There is some change in length when a $33000 ~N$ tensile force is applied on a steel rod of area of cross-section $10^{-3} ~m^2$. The change of temperature required to produce the same elongation,if the steel rod is heated,is (The modulus of elasticity is $3 \times 10^{11} ~N/m^2$ and the coefficient of linear expansion of steel is $1.1 \times 10^{-5} /{ }^{\circ} C$). (in $^{\circ} C$)

What is the reduction electrode potential (in volts) of a copper electrode when $[Cu^{2+}] = 0.01 \ M$ is in a solution at $25^{\circ} C$? ($E^{\circ}$ of $Cu^{2+}/Cu$ electrode is $+0.34 \ V$)

$A$ block of mass $m$ is at rest on another block of the same mass as shown in the figure. The lower block is attached to a spring. What is the maximum amplitude of motion so that both blocks remain in contact?