Two Single Charged Ions Moving Perpendicularly to a Uniform Magnetic

Multiple Choice

Two single charged ions moving perpendicularly to a uniform magnetic field (B = 0.40 T) with speeds of 5000 km/s follow circular paths that differ in diameter by 5.0 cm.What is the difference in the mass of these two ions?

A) 2.6 * 10-28 kg
B) 6.4 * 10-28 kg
C) 3.2 *10-28 kg
D) 5.1 *10-28 kg
E) 1.1 * 10-28 kg