#include <bits/stdc++.h>
using namespace std;
int main() {
  double x1, y1, x2, y2, xn, yn;
  double wx1, wy1, wx2, wy2;
  double v, t, m, d;
  cin >> x1 >> y1 >> x2 >> y2;
  cin >> v >> t;
  cin >> wx1 >> wy1;
  cin >> wx2 >> wy2;
  double l = 0, r = 1e18, eps = 1e-9;
  while (r - l > eps) {
    m = (l + r) / 2;
    if (m <= t) {
      xn = x1 + (wx1 * m);
      yn = y1 + (wy1 * m);
    } else {
      xn = x1 + (wx1 * t);
      xn += (wx2 * (m - t));
      yn = y1 + (wy1 * t);
      yn += (wy2 * (m - t));
    }
    d = sqrt((y2 - yn) * (y2 - yn) + (x2 - xn) * (x2 - xn));
    if (v * m < d)
      l = m;
    else
      r = m;
  }
  cout.precision(9);
  cout << fixed << l;
  return 0;
}
