A positively charged particle of mass 7.2 × 10-8 ???? is traveling due east with a speed of 85 ??/??and enters a 0.31 ?? uniform magnetic field. The particle moves through one-quarter of a circle ina time of 2.2 × 10-3??, at which time it leaves the field heading due south. All during the motionthe particle moves perpendicular to the magnetic field. What is the magnitude of the magnetic force acting on the particle? I tried F=qBvcos of theta but I'm not sure that's the answer. Please help.