Tack för ditt svar.
Jag hittade svaret på b här. Jagfattade det inte helt, kan någon förtydliga.
http://science.howstuffworks.com/question624.htm
To understand how this works, imagine a coaster train reaching the top of a hill. As it ascends, it slows down because gravity is pulling on it from behind. But when the first car makes it over the apex, gravity starts pulling that car down the other side of the hill. Because of gravity's pull, the first car starts to accelerate, which accelerates the second car, which accelerates the third car and so on. In this way, all of the rear cars are accelerated by the motion of the first car, so they all start accelerating at different points along the track.
By the time the last car moves over the hump, gravity has already accelerated the first car a good bit. Consequently, the rear car will have a higher acceleration at the top of the hill than the first car did. This increased force essentially whips the car over the top, briefly pushing up on the riders so that they almost fly out of their seats.
jag förstår inte slutet riktigt, menar de att den sista vagnen "får" en del av alla främre vagnars acceleration?