#include <bits/stdc++.h>
int xa, ya, xb, yb, xv, yv, xw, yw, vm, t;
double l, r, h, x, y, vm2;
int main() {
  scanf("%d%d%d%d", &xa, &ya, &xb, &yb);
  scanf("%d%d%d%d%d%d", &vm, &t, &xv, &yv, &xw, &yw);
  vm2 = 1. * vm * vm;
  xb -= xa;
  yb -= ya;
  l = 0;
  r = 1e9;
  for (int it = 0; it < 200; it++) {
    h = (l + r) * 0.5;
    if (h > t) {
      x = xb - (h - t) * xw - 1. * t * xv;
      y = yb - (h - t) * yw - 1. * t * yv;
    } else {
      x = xb - h * xv;
      y = yb - h * yv;
    }
    if (x * x + y * y > h * h * vm2)
      l = h;
    else
      r = h;
  }
  printf("%.15lf\n", (l + r) * 0.5);
  return 0;
}
