A person knowing elementary physics may think that, if the
dart touches the board, it gets stuck in it.

    Well, the one that wrote this problem failed to consider
this: you'll usually get an equation depeding of t^2. If it has two
positive solutions, you must report "HIT", if for any of them the
dart is inside the board.

    I got stuck with this for 3 days - if I had two positive
solutions, I only checked for the smaller one, and considered the
dart stays there (reality check!!)... well, looks like the dart can
very well get through the board, and then get back in it.