Physics of a melee weapon swing

Game Mechanics
#1

Okay, I need to understand how the physics of this will work.

If the sword is too heavy, the speed you stab with is going to be slower and the attack less effective.

I lunge forward to stab using a knife:
sumFORCE = mass * acceleration-downFORCE(9.8*mass)?

I swing the sword over my head:
Break up the components into 2 vectors, down and forward?

Force of gravity acting upon the object will increase it’s effectiveness for damage depending on it’s mass.

Centripital acceleration is involved?

I swing the sword with my right hand from my left side:
2 component vector, forward and side towards my right.

The gravitational force acting downwards upon the sword will decrease it’s effectiveness depending on the swords mass. A mass of 500Kg will be very heavy and thus slow to swing unless you are incredibly strong.

Can someone please help me with these concepts?

Thank You.

#2

Without modelling various muscle groups and so forth, this is going to be largely an exercise in gross approximation. I would just find an equation that appears to look nice and stick with it. (e.g. speed of blade = a.(strength - k.(weight)) )

The main problem I see with this is that there are many muscle groups in each motion, all of which act on the forces in the blade in different ways to each other. (as a martial artist I can tell you that this also includes abdominal and leg muscles)
Thus shoulder muscles would be using most of their force to counteract the gravitational force, while the back muscles will be almost exclusively pulling the sword sideways. (assuming a man in normal stance, if he is on an angle or something, stuff changes)

I think the idea here should be KISS. Spend your time on things the user will actually notice…

As an example of what I mean…

Basic speed calculation…

Basic Speed BS = a.strength - b.weight
Upward Swing = BS - c.weight
Downward Swing = BS + d.weight
Thrust = BS
Sideways = BS

a,b,c etc = costants. may be replaced with more complex formula to get exponential curves etc if need be.