Which of the following is the simplest amino acid?

Two bodies of $6 \ kg$ and $4 \ kg$ masses have their velocities $5 \hat{i}-2 \hat{j}+10 \hat{k}$ and $10 \hat{i}-2 \hat{j}+5 \hat{k}$ respectively. Then the velocity of their centre of mass is

The concentration of hydrogen ion in a sample of soft drink is $3.8 \times 10^{-3} \, M$. What is its $pH$ (in $.42$)?

The equation of the parabola with focus $(0,0)$ and directrix $x+y=4$ is

If the charge on a capacitor is increased by $2 \, C$,the energy stored in it increases by $21 \%$. The original charge on the capacitor (in coulomb) is

If tangents are drawn from any point on the circle $x^2+y^2=25$ to the ellipse $\frac{x^2}{16}+\frac{y^2}{9}=1$,then the angle between the tangents is