#include <bits/stdc++.h>
using namespace std;
double x[2], y[2], v, t, wx[2], wy[2];
bool calc(double a) {
  double newx = x[0], newy = y[0];
  if (a <= t)
    newx += wx[0] * a, newy += wy[0] * a;
  else
    newx += wx[0] * t + wx[1] * (a - t), newy += wy[0] * t + wy[1] * (a - t);
  if (sqrt(pow(newx - x[1], 2) + pow(newy - y[1], 2)) <= v * a)
    return true;
  else
    return false;
}
int main() {
  for (int i = 0; i < 2; i++) cin >> x[i] >> y[i];
  cin >> v >> t;
  for (int i = 0; i < 2; i++) cin >> wx[i] >> wy[i];
  double l = 0, r = 2e18;
  for (int i = 0; i < 10000; i++) {
    double mid = (l + r) / 2.0;
    if (calc(mid))
      r = mid;
    else
      l = mid;
  }
  printf("%.18lf\n", l);
}
