A man decided to take the trolley to work one day. Along the journey, he discovered that the trolley driver has stepped off the trolley, and now no one was driving it. Determined to reach work on time, the man decided to become the new trolley driver.
As the man approached the road where his office was, he realized that the trolley lacked automatic brakes, and moreover, if the manual brakes were released, then the trolley would resume full speed automatically.
Moreover, the end of the track was ahead, as was a crowd of people, many of whom would be killed (approximately 100), if he stepped off the trolley to go to work.
It would seem the man could simply stay on the trolley to keep it from going. However, the man's job is saving people's lives. If the man did not show up at work exactly on time, 95 people would die.
Furthermore, the doors to the trolley lock as long as the manual brakes are held, so he cannot simply ask a bystander to step on board to solve his dilemma.
How can the man solve his dilemma, and can it be done without anyone being killed? If not, should he let 100 people die who were not otherwise his responsibility, while saving the 95 which is part of his job; or should he let the 95 people die in order to save the 100 which were not his responsibility?
Lastly, whatever he does, all he has on board is a short piece of string, a tennis ball, and an unused bullet - all within reach. All of the windows are locked, and the doors will only open to allow him to exit, but cannot allow another person on.
How does he solve his dilemma?