#include <bits/stdc++.h>
using namespace std;
const int inft = 1000000009;
const int MAXN = 1000006;
int main() {
  int x1, y1, x2, y2;
  scanf("%d%d%d%d", &x1, &y1, &x2, &y2);
  int v, t;
  scanf("%d%d", &v, &t);
  int ax, ay, bx, by;
  scanf("%d%d%d%d", &ax, &ay, &bx, &by);
  double p = 0., k = 1e20;
  for (int i = 0; i < (200); ++i) {
    double m = (p + k) / 2;
    double first = x1, second = y1;
    first += min(m, 1. * t) * ax;
    second += min(m, 1. * t) * ay;
    first += max(0., m - t) * bx;
    second += max(0., m - t) * by;
    first -= x2;
    second -= y2;
    double dist = sqrt(first * first + second * second);
    if (dist < m * v)
      k = m;
    else
      p = m;
  }
  printf("%.9lf\n", p);
  return 0;
}
