The component of vector $\overrightarrow{A} = a_x \hat{i} + a_y \hat{j} + a_z \hat{k}$ along the direction of $\hat{i} - \hat{j}$ is

If $f(t) = \int_{-t}^t \frac{e^{-|x|}}{2} dx$,then $\lim_{t \rightarrow \infty} f(t)$ is equal to:

If a ladder weighing $250\,N$ is placed against a smooth vertical wall and the coefficient of friction between the ladder and the floor is $0.3$,what is the maximum force of friction available at the point of contact between the ladder and the floor?

The formation of the oxide ion $O^{2-}_{(g)}$ requires first an exothermic and then an endothermic step as shown below:
$O_{(g)} + e^- \rightarrow O^{-}_{(g)}$; $\Delta H_{eg} = -142 \ kJ \ mol^{-1}$
$O^{-}_{(g)} + e^- \rightarrow O^{2-}_{(g)}$; $\Delta H_{eg} = +844 \ kJ \ mol^{-1}$
This is because:

Two photons of energy $2.5 \ eV$ and $3.5 \ eV$ fall on a metal surface of work function $1.5 \ eV$. The ratio of the maximum velocities of the photoelectrons emitted from the metal surface is

The maximum velocity of electrons emitted from a metal surface is $V$ when the frequency of light falling on it is $f$. What is the maximum velocity when the frequency becomes $4f$?