Consider an ideal pulley system. If you pull one end of the rope 1m downwards with

3.26 x 1012m/s2
the answer is found using newton's second law, f = ma. the force experienced on the charge in the magnetic field, that is entering perpendicular to the field, the lorentz force is given by f = qvb. equating this with newton's second law, we have ma = qvb. rearranging, a = qvb/m. plug in the values for v, b and m given in the question. q, the coulombic electric charge of the helium nucleus is 2 x (1.6 x 10^-19) as thats the charge of a proton, and a helium nucleus has two protons.