[单选题]
A cyclotron of radius 0.25 m accelerates protons in atl/q; 22hk+2kn-z xvfliteaa/ )fs*k8w5 wr r 1.7-T magneji2oi y1l (ktfed133c sd: f;utic field. What is the kinetic enei1(oyt 1 kcu; :fs2e33lfdjidrgy of the protons when they leave the cyclotron?
A. $7.8 \; keV$
B. $8.7 \; keV$
C. $7.8 \; MeV$
D. $8.7 \; MeV$
Post time 2024-1-22 02:15:01