سؤال قراءة ستيب محلول — الاستنتاج (تدريب 4744)

(1) If you're studying physics, there are few more exhilarating things to learn about than a roller coaster. Roller coasters are driven almost entirely by basic inertial and gravitational forces, all manipulated in the service of a great ride. (2) Roller coasters have a long, fascinating history. The direct ancestors of roller coasters were monumental ice slides that were popular in Russia in the 16th and 17th centuries. (3) Roller coaster historians diverge on the exact evolution of these ice slides into actual rolling carts. The most widespread account is that a few entrepreneurial Frenchman imported the ice slide idea to France. The warmer climate of France tended to melt the ice, so the French started building waxed slides instead, eventually adding wheels to the sleds. (4) The first American roller coaster was the Mauch Chunk Switchback Railway, built in the mountains of Pennsylvania in the mid-1800s. the track, originally built to send coal to a railway, was reconfigured as a "scenic tour." For one dollar, tourists got a leisurely ride up to the top of the mountain followed by a wild, bumpy ride back down. Over the next 30 years, these scenic rides continued to thrive and were joined by wooden roller coasters similar to the ones we know today.