Motion in Combined Electric and Magnetic Fields

Which of the following conditions is used to select charged particles of a particular velocity out of a beam of charges moving with different speeds?

A beam of alpha particles passes undeflected  through a velocity selector having electric and magnetic fields of $120\mathrm{kV}/\mathrm{m}$ and $60 \mathrm{mT}$,

respectively. The velocity of the beam is :

Mention the different fields used in the velocity selector.

Angle between the electric and magnetic field vector in a velocity selector is equal to

In a certain region of space electric field $\stackrel{\rightharpoonup }{\mathrm{E}}$and magnetic field $\stackrel{\rightharpoonup }{\mathrm{B}}$ are normal  to each other and an electron enters in region perpendicular to the direction of both $\stackrel{\rightharpoonup }{\mathrm{B}} \mathrm{and} \stackrel{\rightharpoonup }{\mathrm{E}}$ moves undeflected, then velocity of electron is

Cotyledons are also called-

A velocity selector is used to select alpha particles of energy $200 \mathrm{KeV}$. From a beam containing particles of several energies. The electric field strength is $900 \mathrm{kV} {\mathrm{m}}^{-1}$. What must be the magnetic field strength in $\mathrm{mT}$?