[单选题]
A roller coaster starts from rest at a point 4l,cn ) c.yj*-qdgtm1 f5 m above the bottom of ao) k5o whcen we-1k-.a dip (See Fig. 6-2). Neglect friction, what will be the speed of tneo eo w5aw1c. -khk)-he roller coaster at the top of the next slope, which is 30 m above the bottom of the dip?
