Elastic Motion No Dampening

dist =(targetX - ball_mc._x);
vx = vx + dist*k;
ball_mc._x += vx;

Elastic Motion & Friction

dist =(targetX - ball_mc._x);
vx = vx*f + dist*k;
ball_mc._x += vx;

Elastic Motion & Inertia

dist =(targetX - ball_mc._x);
vx = vx + dist*k*(1/I);
ball_mc._x += vx;

Elastic Motion & Friction & Inertia

dist =(targetX - ball_mc._x);
vx = vx*f + dist*k*(1/I);
ball_mc._x += vx;