#include <bits/stdc++.h>
using namespace std;
int main() {
  int stx, sty, enx, eny, v, t, vx, vy, wx, wy;
  scanf("%d", &stx);
  scanf("%d", &sty);
  scanf("%d", &enx);
  scanf("%d", &eny);
  scanf("%d", &v);
  scanf("%d", &t);
  scanf("%d", &vx);
  scanf("%d", &vy);
  scanf("%d", &wx);
  scanf("%d", &wy);
  double l = 0, r = 100000000;
  for (int i = 0; i < 10000; i++) {
    double m = (l + r) / 2;
    double x = stx, y = sty;
    if (m > t) {
      x += vx * t + wx * (m - t);
      y += vy * t + wy * (m - t);
    } else {
      x += vx * m;
      y += vy * m;
    }
    if (sqrt((enx - x) * (enx - x) + (eny - y) * (eny - y)) < v * m)
      r = m;
    else
      l = m;
  }
  printf("%.8lf\n", l);
  return 0;
}
