#include <bits/stdc++.h>
using namespace std;
template <class T>
inline void si(T &x) {
  register int c = getchar();
  x = 0;
  int neg = 0;
  for (; ((c<48 | c> 57) && c != '-'); c = getchar())
    ;
  if (c == '-') {
    neg = 1;
    c = getchar();
  }
  for (; c > 47 && c < 58; c = getchar()) {
    x = (x << 1) + (x << 3) + c - 48;
  }
  if (neg) x = -x;
}
template <class T>
inline T bigmod(T p, T e, T M) {
  long long ret = 1;
  for (; e > 0; e >>= 1) {
    if (e & 1) ret = (ret * p) % M;
    p = (p * p) % M;
  }
  return (T)ret;
}
template <class T>
inline T gcd(T a, T b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
template <class T>
inline T modinverse(T a, T M) {
  return bigmod(a, M - 2, M);
}
void IN() {
  freopen("in.txt", "r", stdin);
  freopen("out.txt", "w", stdout);
}
const int N = 1001;
struct PT {
  double x, y;
  PT(double x = 0, double y = 0) : x(x), y(y) {}
  PT(const PT &p) : x(p.x), y(p.y) {}
  PT operator+(const PT &p) const { return PT(x + p.x, y + p.y); }
  PT operator-(const PT &p) const { return PT(x - p.x, y - p.y); }
  PT operator*(double c) const { return PT(x * c, y * c); }
  PT operator/(double c) const { return PT(x / c, y / c); }
  void input() { scanf("%lf %lf", &x, &y); }
};
double DIM(PT p) { return sqrt(p.x * p.x + p.y * p.y); }
double val, t;
PT a, b, u, v;
bool can(double Time) {
  PT d = a;
  d = d - u * ((t) > (Time) ? (Time) : (t));
  d = d - v * ((0) > (Time - t) ? (0) : (Time - t));
  if (DIM(d) <= Time * val)
    return 1;
  else
    return 0;
}
int main() {
  a.input();
  b.input();
  cin >> val >> t;
  a = b - a;
  u.input();
  v.input();
  double lo = 0, hi = 1e12, mid, ans = -1;
  for (int i = 0; i < 500; i++) {
    mid = (lo + hi) / 2;
    if (can(mid)) {
      ans = mid;
      hi = mid;
    } else
      lo = mid;
  }
  printf("%.10lf\n", ans);
  return 0;
}
