A Proton Is Projected at a Stationary ${ } _ { 88 } ^ { 226 }$

Multiple Choice

A proton is projected at a stationary ${ } _ { 88 } ^ { 226 }$ Ra aluminum target. The proton momentarily comes to a halt at a distance from the center of an aluminum nucleus, equal to twice the nuclear radius. Assume that the nucleus retains its spherical shape and that the nuclear force on the proton is negligible. The initial kinetic energy of the proton, in $\mathrm { MeV }$ , is closest to:

A) $5.8 \mathrm { MeV }$
B) $2.9 \mathrm { MeV }$
C) $8.7 \mathrm { MeV }$
D) $13 \mathrm { MeV }$
E) $17 \mathrm { MeV }$