Physical force is a poor first choice for sure. (Tone of voice, etc.)
A poor second as well. (Timeouts etc.)
A poor n'th as long as reasonable alternatives for escalation exist at step n.
Eventually all discipline comes down to physical force. If nothing else, then force in the form of police officers and jails. However there is no need to be in a hurry to go to those limits, and the use of discipline should not be the primary focus of parenting. (IMHO of course.)
What is funny is how many people can hear and accept that this has been discovered to apply for, say, dogs but then won't accept that it applies to their own children...
Cheers,
Ben