Question

Determine the magnitude and direction of the magnetic force on a proton
moving to the north at 8.6 x 104 m/s, as it enters a magnetic field of 1.2 T,
pointing vertically up, out of the page.
(the arrow is towards north)

Answer 1

According to the left hand rule, the Lorenz's force will be directed to the right, the magnitude will be

$$F=qvB=\\=1.602\cdot10^{-19}\cdot8.6\cdot10^4\cdot1.2=1.7\cdot10^{-15}\text{ N}.$$