#include <bits/stdc++.h>
using namespace std;
long double X1, X2, Y1, Y2, x, y, ux, uy, wx, wy, umax, t;
bool check(long double time) {
  long double t1 = min(time, t);
  long double t2 = max(time - t, (long double)0);
  long double x = X1 + t1 * ux + t2 * wx;
  long double y = Y1 + t1 * uy + t2 * wy;
  long double distance = sqrt((x - X2) * (x - X2) + (y - Y2) * (y - Y2));
  if (umax * time + 0.00000000001 > distance)
    return 1;
  else
    return 0;
}
int main() {
  cin >> X1 >> Y1 >> X2 >> Y2;
  cin >> umax >> t;
  cin >> ux >> uy >> wx >> wy;
  x = X2 - X1;
  y = Y2 - Y1;
  long double l = 0, r = (long double)1e8;
  for (int i = 0; i < 100; ++i) {
    long double m = (l + r) / 2.0;
    if (check(m))
      r = m;
    else
      l = m;
  }
  cout << fixed << setprecision(10) << r << '\n';
  return 0;
}
