A proton and a neutron are each close to a positive nucleus. How does the charge on the nucleus affect the proton and the neutron, if at all?
A The neutron is attracted; the proton is repelled.
B The neutron is not affected; the proton is repelled.
C The proton is attracted; the neutron is repelled.
D The proton is not affected; the neutron is repelled.

Two steel balls, each of mass m, are welded to a light rod of length l and negligible mass and are initially at rest on a smooth horizontal surface. a horizontal force of magnitude f is suddenly applied to the rod as shown. determine (a) the instantaneous acceleration a of the mass center g and (b) the corresponding rate at which the angular velocity of the assembly about g is changing with time.