  We present two results in the treatment of self-force of accelerating bodies.
If the total force on an extended rigid object is calculated from the change of
momentum summed over planes of simultaneity of successive rest frames, then we
show that an ideal fluid, moving rigidly, exerts no net force on its boundary.
Under this same definition of total force, we find the electromagnetic
self-force for a spherical charged shell of proper radius R accelerating with
constant proper acceleration g is (2 e^2 g/R)[ 1/12 - \sum_{n=0}^\infinity (g
R)^{2n} ((2n-3)(2n-1)(2n+1)^2)^{-1} ].
