Does the strong (nuclear) force ever contribute to decay? Does the strong (nuclear) force ever contribute to decay ?
Or is the weak nuclear force the only decaying force ?
 A: Most of the resonances detected  in particle physics scattering experiments are bound states of the strong force, bound for a time interval before  decay .
These are created in the interaction and seen in invariant mass combinations of the interaction products, statistically.
The distinction with electromagnetic or weak decays comes from the widths of the resonances: the strong decays have MeV widths, whereas weak and electromagnetic decays are at the experimental error.Tables of delta resonances and N resonances  etc can be found in the particle data booklet.

Here the invariant mass of a proton K pair shows a  lamda resonance induced by the strong force.
A: The difference between strong force decay and weak force decay is that the strong force decay is applicable to only quarks. Also the quarks have to be the same flavor. For example the flavor should be say up quark and antiup quark. They will annihilate into a gluon and that gluon can decay into other quarks. Also the weak force could theoretically annihilate two quarks that are in the same generation but have different charges. The weak force is usually involved in decays. However when the strong force is involved the decays happen much faster. This is because the strong force is the strongest force.  
