My old Physics teacher at school (Mr Briggs, if anyone knows him), posed a similiar question when I was about 12! His version was; a smart monkey hanging from a branch in a tree watches a hunter aiming at him and thinks 'as soon as I see the flash, I'll let go and drop, and the hunter will miss'. The hunter who didn't have any sights on his gun, was aiming along the barrel and assuming a flat trajectory for the bullet. So.. the gun goes off, the monkey drops, and to his surprise gets shot; as the monkey and bullet accelerate towards the ground at the same rate. This was so enlightening as a 12 year old, that the motion could be resolved into simple components and introduced determinism to a young inquisitive mind.