I'm sure many readers would have heard of this one: Trolley Problem.
A fast, unstoppable trolley is heading towards 5 people stuck in its track. You are within reach of a lever which, when pulled, will change the path of the trolley to another track, with 1 person on it. If you pull the lever, the trolley will strike and kill 1 person, rather than 5 of them. Will you do it?
Sometimes, I like to state the obvious - so, here it is: it isn't moral or immoral to decide either way. The problem is designed such that responses from subjects help scientists understand cognitive processes, logical reasoning, emotional irrationality and stuff (I'm not a social scientist =P)
I assume you've made your choice. If you decided sacrificing 1 life to save 5 makes a better option, I'm sure many others feel the same. Let's try again:
A fast, unstoppable trolley is heading towards 5 people stuck in its track. You are within reach of a fat man, who you can push onto the track, into the way of the trolley. The trolley, striking (and therefore, killing) him, will stop short of crashing into the 5 people. Will you do it?
The outcome will be exactly the same as the first scenario: 1 life for 5, or not? However, a lot more people will have difficulty making the decision.
I had, many years ago, read a more interesting version:
You are driving a high-speed train. Ahead of you, you see 5 children playing on the track, in the way of the train. You will not be able to stop the train in time, but you are within reach of a lever to divert the train to an adjacent track which is no longer in use, to avoid them. However, on this abandoned track, there is a lone child playing. Will you pull the lever?