71 Roller Coasters-Mid

Roller Coasters FOCUS Question How do forces make a roller coaster car move along its track?

过山车焦点问题力是如何使过山车沿着轨道移动的?

The Thrill of the Ride Ka-thunk! The restraints press down across your body, holding you down in your seat. Ka-CHINK-chink-chink. The small car lurches forward and you start to climb up, up, up, up to dizzying heights. For a moment, at the top of the world, you feel you can almost touch space. Then the world falls out from under you, and you plummet toward Earth. Your skin tingles and you scream and laugh as the ride picks up speed, thundering down the track. Your roller coaster ride is two to three minutes of mind-bending, gut- sucking forces and nonstop changes in acceleration. Roller coasters put Newton's laws of motion into action! Let's explore the physics that make roller coasters fun.

骑马的快感咔咔!束缚压在你的身体上，把你压在座位上。 Ka-CHINK-chink-chink。小车蹒跚向前，你开始往上爬，往上爬，往上爬，爬到令人眼花缭乱的高度。 有那么一瞬间，在世界之巅，你几乎可以触摸到太空。 然后世界就会从你身下坠落，你就会坠向地球。 你的皮肤发麻，你尖叫着笑着，因为过山车加快了速度，轰隆隆地沿着轨道行驶。 你的过山车之旅是两到三分钟的令人费解的、吸肠的力量和不间断的加速度变化。 过山车将牛顿运动定律付诸实践!让我们来探索一下让过山车变得有趣的物理原理。

Riding with Newton At the beginning of the ride, you climbed into a coaster car, eager for it to start. Did you know that even before the cars moved, the laws of motion were already at work? Newton's law of inertia says that an object at rest will remain at rest until a force moves it. It also says that an object in motion will stay in motion until a force stops it. The measure of an object's motion is called momentum. On most roller coasters, a motor makes a chain pull the car up that first hill. The motor and chain provide the force to overcome the car's inertia.

在旅程的开始，你爬进过山车车厢，渴望它启动。 你知道吗，在汽车开动之前，运动定律就已经在起作用了? 牛顿惯量定律说，静止的物体将保持静止，直到有一个力使它运动。 它还说，运动中的物体会一直保持运动，直到有一个力使它停止。 物体运动的量度叫做动量。 在大多数过山车上，一个马达使链条将汽车拉上第一个山坡。 马达和链条提供了克服汽车惯性的力量。

The Lift Hill When the car pulls out of the station, it is immediately pulled up a huge hill. Why is the hill so high? That first hill lifts the car to its highest point of the whole ride, which is why that hill is called the "lift hill." Way up there, the car has the most potential energy, or stored energy. Gravity is always pulling the car down toward the ground, and the lift hill gives the car a long way to pick up speed as it rolls down. Believe it or not, most roller coasters only use motors to get the car up the lift hill. After that, it rolls—or coasts— the rest of the way due to gravity and inertia.

电梯山当汽车驶出车站时，它立刻被拉上一座大山。 为什么这座山这么高?第一个山头会把汽车提升到整个旅程的最高点，这就是为什么那个山头被称为“升降机山”。 在这上面，汽车拥有最大的势能，或者说储存的能量。 重力总是把汽车拉向地面，电梯山给了汽车很长的一段路来加快它向下滚动的速度。 信不信由你，大多数过山车只用马达让车爬上缆车山。 在这之后，由于重力和惯性，它可以滑行。

Picking Up Speed Once the car tips over the hill, it speeds down the track. The potential energy the car had at the top changes to kinetic energy, or the energy of motion. It quickly accelerates or gets faster and faster. At the bottom of the hill, most of the car's potential energy. has changed to kinetic energy You quickly start climbing another hill. It's not as tall as the first one, but it's still pretty high. As the car climbs, gravity pulls down on it, reducing its speed. The car's momentum carries it up to the top of the hill. The car's kinetic energy changes back into potential energy as it climbs the second hill.

汽车一旦翻了山，就会沿着轨道加速行驶。 汽车顶部的势能变成了动能，或者说是运动能量。 它迅速加速或变得越来越快。 在山脚下，汽车的大部分势能。 你很快开始爬另一座山。 它没有第一个那么高，但仍然很高。 当汽车爬升时，重力向下拉它，降低它的速度。 汽车的冲力把它带到了山顶。 当汽车爬上第二座山时动能又变回势能。

Loopy Down the hill and up ahead, the track seems to turn upside down. So does your stomach! How will the car ever get through that loop? The car is moving very fast when it enters the loop; it still has a lot of momentum. The car's kinetic energy changes back to potential energy as it rolls up the loop. But what happens next? Gravity pulls on the car, and potential energy switches to kinetic energy once more. Down the loop you go! Do You Know? Roller coaster loops are often shaped like an upside-down raindrop. With a steeper slope at the bottom. the car enters and exits the loop faster than it would in a circle.

下了山，往上走，跑道似乎颠倒了。 你的胃也是!这辆车要怎么通过那个循环? 当汽车进入环路时，它移动得非常快;它仍然有很大的动力。 汽车在绕圈的过程中动能又变回势能。 但接下来会发生什么?重力作用于汽车，势能再次转化为动能。 你去循环!你知道吗? 过山车的环通常形状像一个倒置的雨滴。 底部坡度更陡。 汽车进入和退出环的速度比在一个圈中要快。