The magnetic field of the Earth at acertain location is directed vertically downward and has amagnitude of 50.0 μT. A proton is moving horizontallytoward the west in this field with a speed of 6.20 ×106 m/s. (a) What are the direction andmagnitude of the magnetic force the field exerts on this charge?(b) What is the radius of the circular arcfollowed by this proton?