The Roller Coaster Twist

" Look, Dad! ” Lila said, waving a flyer. " The amusement park is having a roller coaster design contest. First prize is two tickets for the first ride on the new coaster! ” Dad leaned back and pretended he was riding a roller coaster. " I love when I’m pushed back in the seat. ” " It only feels like you’re being pushed back. The seat is really pushing you forward. ”

"看，爸爸！”莉拉挥舞着传单说。 "游乐园正在举行过山车设计比赛。 一等奖是两张新过山车第一次乘坐的票！” 爸爸向后倾斜，假装他在坐过山车。 "我喜欢被推回座位的感觉。” "感觉就像你被推了回去。这个座位真的把你推向了前方。”

Dad laughed. “ You sure know your stuff! ” Lila started drawing ideas. First she drew a lift hill. She knew that roller coasters didn’t have motors. The cars gained speed as gravity pulled them down from the top of the lift hill. This momentum would carry the cars through the rest of the roller coaster.

爸爸笑了。“你肯定知道你的东西！” 莉拉开始构思。首先，她画了一个上坡。 她知道过山车没有马达。 汽车在重力的作用下从升降山顶下降，速度加快。 这种势头将使汽车在过山车的其余部分行驶。

" My hill looks too short, ” Lila thought. " The cars won’t have enough momentum to go through loops or over hills. ” She made the hill a bit taller. If she made it too tall, the cars would gain too much speed. Then the ride would be uncomfortable or dangerous. After the lift hill, Lila added loops, hills, and curves. " Yes! ” Lila declared. She was almost ready to build a model!

"我的山看起来太短了，”莉拉想。 "这些汽车将没有足够的动力穿过环路或越过山丘。” 她把山修得高了一点。如果她把它弄得太高，汽车就会超速。 那么乘坐会不舒服或危险。 在电梯坡道之后，Lila增加了环路、坡道和弯道。 "是的！”莉拉宣布。她几乎准备好做模特了！

As Dad drove to the park, Lila practiced explaining her model. " Gravity pulls you down at the top of the loop, but the momentum keeps pushing you forward. ” " That gives you the weightless feeling?” Dad asked.

当爸爸开车去公园时，莉拉练习着解释她的模特。 "重力会把你拉到环的顶端，但动量会继续推动你前进。” "这给你一种失重的感觉？”爸爸问。

" Exactly. ” Dad parked. As Lila started to get out of the car, the box slipped from her hands. Lila gasped as her model crashed onto the pavement. " It’s ruined! What am I going to do? Judging starts soon! ” Dad helped her pick up the pieces. “ It’s not too bad. You’ll think of something. ”

"没错。”爸爸停车了。当莉拉开始下车时，箱子从她手中滑落。 当她的模特撞上人行道时，莉拉气喘吁吁。 "它毁了！我该怎么办？裁判很快就开始了！” 爸爸帮她捡起了碎片。“还不错。你会想办法的。”

In the waiting room, Lila examined the other contestants’ designs. Some wouldn’t work, but others were good. She stared at the pieces of her model in the box. " Hey! ” she thought suddenly. “ Maybe I can put the pieces together as I explain my model! ” Soon it was Lila’s turn. In the judging room, Lila put the lift hill on the table. “ A cable pulls the cars to the top. ”

在等候室里，莉拉检查了其他参赛者的设计。 有些不起作用，但有些很好。 她凝视着盒子里的模型碎片。 "嘿！”她突然想。“也许我可以在解释我的模型时把这些碎片放在一起！” 很快轮到莉拉了。在裁判室，