On watching The Dark Knight (2008) again, I was struck withinspiration for a physics problem. In their final confrontation,Batman throws the Joker off of a high building. Half-way down tothe ground Batman launches his grapple gun and barely manages tohook Joker and prevent him from hitting the ground. If the buildingwere 100 meters tall, how fast would the grapple gun need to befired in order to catch the Joker before he hits the ground,assuming Batman waits until the Joker is half-way down to fire? Asusual, ignore air resistance. How fast was Joker moving just priorto being bat-grappled?
