#include <bits/stdc++.h>
using namespace std;
double const eps = 1e-7;
double dis(double x1, double y1, double x2, double y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
int main() {
  double x1, y1, x2, y2;
  double v, t, vx, vy, wx, wy;
  cin >> x1 >> y1 >> x2 >> y2;
  cin >> v >> t >> vx >> vy >> wx >> wy;
  double l = 0, r = t, mid;
  double ans = -1;
  while (l + eps < r) {
    mid = (l + r) * 0.5;
    double tx = x1 + mid * vx, ty = y1 + mid * vy;
    double d = dis(tx, ty, x2, y2);
    if (v * mid + eps > d) {
      ans = mid;
      r = mid;
    } else {
      l = mid;
    }
  }
  if (ans < 0) {
    x1 += t * vx, y1 += t * vy;
    l = 0, r = 1e10;
    while (l + eps < r) {
      mid = (l + r) * 0.5;
      double tx = x1 + mid * wx, ty = y1 + mid * wy;
      double d = dis(tx, ty, x2, y2);
      if (v * (t + mid) + eps > d) {
        ans = mid + t;
        r = mid;
      } else
        l = mid;
    }
  }
  printf("%.10lf\n", ans);
  return 0;
}
