#include <bits/stdc++.h>
using namespace std;
const int maxn = 5E5 + 5, mod = 1e9 + 7;
double x1, y11, x2, y2, x3, y3, g3;
double v, t1;
double vx1, vy1, vx2, vy2, g1, g2;
bool work(double t) {
  double x, y;
  if (t < t1) {
    x = x1 + vx1 * t;
    y = y11 + vy1 * t;
    double l1, l2, l3;
    l1 = (x1 - x2) * (x1 - x2) + (y11 - y2) * (y11 - y2);
    l2 = (x1 - x) * (x1 - x) + (y11 - y) * (y11 - y);
    l3 = (x - x2) * (x - x2) + (y - y2) * (y - y2);
    if (l3 <= l2 && l1 <= l2) return true;
    if (sqrt(l3) <= v * t) return true;
    return false;
  }
  double t2 = t - t1;
  x = x1 + vx1 * t1 + vx2 * t2;
  y = y11 + vy1 * t1 + vy2 * t2;
  double l1, l2, l3;
  l1 = (x1 - x2) * (x1 - x2) + (y11 - y2) * (y11 - y2);
  l2 = (x1 - x) * (x1 - x) + (y11 - y) * (y11 - y);
  l3 = (x - x2) * (x - x2) + (y - y2) * (y - y2);
  if (l3 <= l2 && l1 <= l2) return true;
  if (sqrt(l3) <= v * t) return true;
  return false;
}
int main() {
  cin >> x1 >> y11 >> x2 >> y2;
  x3 = x2 - x1;
  y3 = y2 - y11;
  cin >> v >> t1;
  cin >> vx1 >> vy1 >> vx2 >> vy2;
  double ans, l = 0, r = 1e9;
  while (l + (1e-8) < r) {
    double mid = (l + r) / 2;
    if (work(mid)) {
      r = mid;
    } else {
      l = mid;
    }
  }
  printf("%.15f\n", l);
}
