#include <bits/stdc++.h>
using namespace std;
const int MAX = 510;
int n, m;
double xa, ya, x2, y2;
double v, vx1, vx2, vy1, vy2, t;
int check(double k) {
  double x, y;
  x = xa + vx1 * min(k, t) + vx2 * max(0.0, k - t);
  y = ya + vy1 * min(k, t) + vy2 * max(0.0, k - t);
  double dist = sqrt((x - x2) * (x - x2) + (y - y2) * (y - y2));
  if (v * k >= dist) return 1;
  return 0;
}
int main() {
  int i, j, k;
  while (~scanf("%lf%lf%lf%lf", &xa, &ya, &x2, &y2)) {
    scanf("%lf%lf", &v, &t);
    scanf("%lf%lf", &vx1, &vy1);
    scanf("%lf%lf", &vx2, &vy2);
    double l = 0.0, r = 1e9;
    while ((r - l) > 1e-6) {
      double mid = (l + r) / 2;
      if (check(mid))
        r = mid;
      else
        l = mid;
    }
    printf("%.10lf\n", l);
  }
  return 0;
}
