#include <bits/stdc++.h>
const double pi = acos(-1);
using namespace std;
double x[2], y[2], sx, sy;
double v, t;
double vx[2], vy[2];
double dis(double a, double b, double x, double y) {
  return sqrt((a - x) * (a - x) + (b - y) * (b - y));
}
bool judge(double t0) {
  if (t0 <= t) {
    sx = x[0] + vx[0] * t0;
    sy = y[0] + vy[0] * t0;
    if (v * t0 >= dis(sx, sy, x[1], y[1])) return true;
  } else {
    sx = x[0] + vx[0] * t + vx[1] * (t0 - t);
    sy = y[0] + vy[0] * t + vy[1] * (t0 - t);
    if (v * t0 >= dis(sx, sy, x[1], y[1])) return true;
  }
  return false;
}
int main() {
  for (int i = 0; i < 2; i++) scanf("%lf%lf", &x[i], &y[i]);
  scanf("%lf%lf", &v, &t);
  for (int i = 0; i < 2; i++) scanf("%lf%lf", &vx[i], &vy[i]);
  double l = 0, r = 1e8, m;
  for (int i = 0; i < 400; i++) {
    m = (l + r) / 2;
    if (judge(m))
      r = m;
    else
      l = m;
  }
  printf("%.10f\n", l);
  return 0;
}
