At What Speed Would a Proton Need to Circle the Earth

Short Answer

At what speed would a proton need to circle the Earth at a height of 1000 km above the equator if the Earth's magnetic field is horizontal and directed north-south, with an intensity of 4.00 × 10−8 T? (The radius of the Earth is 6400 km and the charge and mass of the proton are q = 1.60 × 10−19 C and mp = 1.67 × 10−27 kg. Ignore relativistic corrections.)