#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-8;
double sx, sy, ex, ey;
double v, t;
double vx, vy, wx, wy;
bool judge(double h) {
  if (h > t) {
    sx = ex - vx * t - (h - t) * wx;
    sy = ey - vy * t - (h - t) * wy;
  } else {
    sx = ex - vx * h;
    sy = ey - vy * h;
  }
  return sx * sx + sy * sy <= v * v * h * h;
}
int main() {
  scanf("%lf%lf%lf%lf", &sx, &sy, &ex, &ey);
  scanf("%lf%lf", &v, &t);
  scanf("%lf%lf%lf%lf", &vx, &vy, &wx, &wy);
  ex -= sx, ey -= sy;
  double l = 0, r = 1e20;
  while (r - l > eps) {
    double mid = (l + r) * 0.5;
    if (judge(mid))
      r = mid;
    else
      l = mid;
  }
  printf("%.10lf\n", l);
  return 0;
}
