Power, Strength, and Force

Teaching Arendt today right after the President's speech on Afghanistan, so this seemed like a good question. In the social/political context, what is the difference between power, strength, and force? We tend to use the words interchangeably, but are they really synonymous? It seems that you can show strength without using force. The weak can have power, surely, indeed sometimes the weakness can be a source of power. So what's the difference?