#include <bits/stdc++.h>
namespace YGGGAY {
double sx, sy, tx, ty, vx, vy, wx, wy, vmax;
int t;
inline bool check(register double tmp) {
  register double tmpx = sx, tmpy = sy;
  tmp < t ? (tmpx += tmp * vx, tmpy += tmp * vy)
          : (tmpx += t * vx + (tmp - t) * wx, tmpy += t * vy + (tmp - t) * wy);
  tmpx = tx - tmpx, tmpy = ty - tmpy;
  return (tmpx * tmpx + tmpy * tmpy) / tmp / tmp <= vmax * vmax + 1e-9;
}
inline void main() {
  register double l = 0, r = 1 << 30, mid;
  scanf("%lf %lf %lf %lf %lf %d %lf %lf %lf %lf", &sx, &sy, &tx, &ty, &vmax, &t,
        &vx, &vy, &wx, &wy);
  while (r - l > 1e-9) check(mid = (l + r) / 2.0) ? r = mid : l = mid;
  printf("%.9lf\n", mid);
}
}  // namespace YGGGAY
int main() {
  YGGGAY ::main();
  return 0;
}
