Yes, in this case the equation refers to the average force over an interval of time: if at time instant A we had a speed v1 and at a later instant B we have some speed v2 then a force with a magnitude of at least m * (v2 - v1) / (tB - tA) must have acted, therefore the analysis should hold.
As you point out the area is very important in the analysis, since Pressure = F / A. For large areas the force "spreads out" and the damage is less.
The fatality of the accident can vary due to many circumstances however I think we can safely assume that for the purposes of our initial analysis, 5 lbs traveling at 30mph and crashing into my head is not something I am looking forward to ;)
As you point out the area is very important in the analysis, since Pressure = F / A. For large areas the force "spreads out" and the damage is less.
The fatality of the accident can vary due to many circumstances however I think we can safely assume that for the purposes of our initial analysis, 5 lbs traveling at 30mph and crashing into my head is not something I am looking forward to ;)