In a certain 2 -inputs logic gate, when inputs $\mathrm{A}=0$ and $\mathrm{B}=0$, then output $\mathrm{C}=1$. And also when inputs $\mathrm{A}=0, \mathrm{~B}=1$, then again output $\mathrm{C}=1$. The gate must be

The vector sum of two forces $\vec{A}$ and $\vec{B}$ is perpendicular to their vector difference. Hence forces $\vec{A}$ and $\vec{B}$ are

In the following circuit, current through ACB if each resistance $\mathrm{R}=4 \Omega$ is

A particle is performing S.H.M. starting from extreme position. Graphical representation shows that between displacement and acceleration, there is a phase difference of