Who developed quantum mechanics?

Which of the following rules states that it is impossible to determine simultaneously the exact position and exact momentum of an electron?

Calculate the uncertainty in the position of an electron $(mass = 9.1 \times 10^{-28} \ g)$ moving with a velocity of $3 \times 10^4 \ cm \ sec^{-1}$,if the uncertainty in velocity is $0.011 \%$ (in $cm$)?

The measurement of the electron position is associated with an uncertainty in momentum,which is equal to $1 \times 10^{-18} \ g \ cm \ s^{-1}$. The uncertainty in electron velocity is (mass of an electron is $9 \times 10^{-28} \ g$):

Give the difference between $\psi$ and $|\psi|^2$.

If the uncertainty in momentum of a particle is twice the uncertainty in its position,what will be the uncertainty in the position of the particle?