float second = step*TimeInc;

float dragRate = 1 - Drag*TimeInc/@mass;

float dragingInTime = ( pow(dragRate,step) - 1 ) / (dragRate - 1);

vector constantPos = @v*TimeInc * dragingInTime;

vector accelPos = g*pow(TimeInc,2) * ( (step-dragingInTime) / (1-dragRate) );

@P += constantPos + accelPos;

@v = @v*pow(dragRate,step) + g*TimeInc*dragingInTime;