[单选题]
A cyclotron of radius 0.gea9( )8xgmu/3qxix y 25 ybmvgadl 2o59wl7um ladp5 ,y90)yf/m accelerates protons in a 1.7-T magnetic field. What is the kinetic energy of the protons when they lgvom/lm9lyayld 07p2 awybf9 55d) ,ueave 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