#include <bits/stdc++.h>
using namespace std;
int x_1, y_1, x2, y2, v, t, vx, vy, wx, wy;
double dis(double x, double y) {
  return sqrt((x - x2) * (x - x2) + (y - y2) * (y - y2));
}
bool test(double tempo) {
  double xx_1 = x_1;
  double yy_1 = y_1;
  if (tempo > t) {
    xx_1 += t * vx + (tempo - t) * wx;
    yy_1 += t * vy + (tempo - t) * wy;
  } else {
    xx_1 += tempo * vx;
    yy_1 += tempo * vy;
  }
  return (double)dis(xx_1, yy_1) / (double)v <= tempo;
}
double bs(double lo, double hi) {
  for (int i = 0; i < 200; ++i) {
    double mid = (hi + lo) / 2.0;
    if (test(mid)) {
      hi = mid;
    } else {
      lo = mid;
    }
  }
  return lo;
}
int main(void) {
  cin >> x_1 >> y_1 >> x2 >> y2;
  cin >> v >> t;
  cin >> vx >> vy >> wx >> wy;
  cout << fixed << setprecision(8) << bs(0, 100000000) << "\n";
  return 0;
}
