Nudges have two different active knockback vectors.
For shield:
Strength / 3 + Shield skill * 2 for both the initial raw damage and knockback, then each nudge has another multiplier (defense nudge has a 10x and 3x multiplier to the 2 knockback vectors, but damage / 5 for instance). Finally, there is one last penalty against defending/non-attacking opponents, knockback / 4 against defenders, and knockback / 2 against non-attackers.
Others have the same penalties against defenders/non-attackers, but they have strength * 10 and strength * 30 for initial knockback vectors.