Hm. A solid rocket burns from one end, opening up the nose will do nothing to the thrust. Splitting a side, I would guess, will lead to uncontrolled acceleration with chaotic flight path, but not zero acceleration.
Apparently that's true of some model rocket motors, but the SRBs have a hollow through the entire length of the propellant, so that it burns from the center out to the casing along the entire length at the same time.
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