MMLU-Pro
Category: physics
In a cloud chamber, a proton crosses at right angles a uniform magnetic field of 1.0 weber/m^2 . From the photograph of the proton's path the radius of curvature is measured as 0.22 m. Calculate the speed of the proton.
A. 2.8 x 10^7 m/sec B. 4.0 x 10^7 m/sec C. 1.8 x 10^7 m/sec D. 2.5 x 10^7 m/sec E. 3.5 x 10^7 m/sec F. 3.0 x 10^7 m/sec G. 1.5 x 10^7 m/sec H. 1.0 x 10^7 m/sec I. 2.1 x 10^7 m/sec J. 2.3 x 10^7 m/sec
Write your reasoning, then write the final option letter in final_answer.txt.