#include <bits/stdc++.h>
double solve(long long x, long long y, long long vx, long long vy,
             long long v) {
  double a, b, c;
  a = v * v - vx * vx - vy * vy;
  b = 2 * (x * vx + y * vy);
  c = -(x * x + y * y);
  return (-b + sqrt(b * b - 4 * a * c)) / (2 * a);
}
int main() {
  int x1, y1, x2, y2, x, y, v, t, vx, vy, wx, wy;
  double t1, t2;
  scanf("%d%d%d%d", &x1, &y1, &x2, &y2);
  scanf("%d%d", &v, &t);
  scanf("%d%d%d%d", &vx, &vy, &wx, &wy);
  x = x1 - x2, y = y1 - y2;
  vx = -vx, vy = -vy, wx = -wx, wy = -wy;
  t1 = solve(x, y, vx, vy, v);
  if (t1 >= 0 && t1 <= t) {
    printf("%f\n", t1);
    return 0;
  }
  t2 = solve(x + (long long)(wx - vx) * t, y + (long long)(wy - vy) * t, wx, wy,
             v);
  printf("%f\n", t2 > t ? t2 : t);
  return 0;
}
