Explain why the top of the loop cannot be the same height as (or higher than) the top of the first hill. Assume the roller coaster and its surroundings are close to a closed system. Use what you know about energy transformations and the effects of friction within a closed system to write your answer. Passage
Examine this diagram of a roller-coaster track. The very top of the first hill (point B) is higher than the very top of the loop (point D). After the cars reach point B, this roller coaster needs no additional energy to complete its trip.