#include <bits/stdc++.h>
using namespace std;
pair<long double, long double> a, b, v, w;
long double mx;
long double t;
bool valid(long double tim) {
  pair<long double, long double> p;
  p.first = b.first;
  p.first -= min(t, tim) * v.first;
  p.first -= max(tim - t, (long double)0) * w.first;
  p.second = b.second;
  p.second -= min(t, tim) * v.second;
  p.second -= max(tim - t, (long double)0) * w.second;
  return (tim * mx) >= sqrt((p.first - a.first) * (p.first - a.first) +
                            (p.second - a.second) * (p.second - a.second));
}
int main() {
  ios::sync_with_stdio(false);
  cout.precision(15);
  cout << fixed;
  cin >> a.first >> a.second >> b.first >> b.second;
  if (a.first == b.first && a.second == b.second) {
    cout << (long double)(0) << "\n";
    return 0;
  }
  cin >> mx >> t;
  cin >> v.first >> v.second >> w.first >> w.second;
  long double l = 0, r = 1e12;
  for (int i = 0; i < 100000; i++) {
    long double mid = (l + r) / 2;
    if (valid(mid))
      r = mid;
    else
      l = mid;
  }
  cout << r << "\n";
  return 0;
}
