79 Simple and Complex Machines-High

Simple and Complex Machines Written by Ned Jensen

简单机器和复杂机器，作者:Ned Jensen

Introduction How do you do work? How do you eat cereal or hit a baseball really far? How do you slice cheese for a sandwich or loosen the lid of a jar? You probably use tools. People have been making and using tools for millions of years. We create tools to make work easier to do. A machine is a device that uses energy to help us do work. Tools that have only a few parts are called simple machines. Hammers and knives are simple machines. Some machines combine several simple machines. Clocks and bicycles are complex machines. In this book, you will learn about machines and how they make work easier.

你是怎么工作的? 你怎么吃麦片，怎么把棒球打得很远? 你如何为三明治切奶酪或打开罐子的盖子? 你可能会使用工具。数百万年来，人们一直在制造和使用工具。 我们创造工具是为了让工作更容易。 机器是一种利用能量帮助我们做功的装置。 只有几个零件的工具叫做简单机器。 锤子和刀都是简单的机器。 有些机器由几台简单的机器组合而成。 钟表和自行车都是复杂的机器。 在这本书中，你将了解机器以及它们如何使工作更容易。

Do You Know? Animals use tools, too! Apes use sticks to get ants out of anthills. Otters use rocks to crack open clamshells. Crows can make wire hooks to get food out of a tall, thin container. In the introduction, you learned that machines make work easier. But what do we mean by work? In science, work is done whenever an object is moved over a distance. To move something, you must use force. The more force it takes to move an object, the more work is done. The greater the distance the object moves, the greater the amount of work it takes to move it. Whenever you push, pull, turn, or lift an object, you are using force to move it. The amount of force it takes depends on the weight of the object. It takes a lot more force to move a large boulder than to move a small rock. Machines make work easier by reducing the amount of force, or effort, it takes to move an object, or load.

你知道吗?动物也使用工具!猿用棍子把蚂蚁赶出蚁丘。 水獭用石头敲开蛤壳。 乌鸦可以用铁丝钩从又高又薄的容器里取出食物。 在介绍中，您了解到机器使工作更容易。 但是功是什么意思呢? 在科学中，只要物体移动一段距离，就做功。 要移动某物，你必须用力。 移动物体所需要的力越大，所做的功就越大。 物体移动的距离越大，移动它所需要的功就越大。 无论何时你推、拉、转或举起一个物体，你都是在使用力来移动它。 它所需要的力取决于物体的重量。 移动一块大石头比移动一块小石头需要更大的力。 机器通过减少移动物体或负载所需的力或力来简化工作。

But there is a trade-off when you use a machine to reduce the force it takes to do work. The trade-off is that you have to apply the force over a greater distance. Most machines help you do work by spreading out the force over a larger distance.

但是，当你使用机器来减少做功所需的力时，这是一种权衡。 代价是你必须在更大的距离上施加力。 大多数机器通过将力分散到更大的距离来帮助你做功。

Types of Simple Machines There are only a few types of simple machines. Some have no moving parts, and others have only a few. Below are the seven simple machines you will read about in this book.

简单机器的种类只有几种。 有的没有活动部件，有的只有几个。 以下是你将在这本书中读到的七种简单的机器。

Inclined Plane The inclined plane is a very simple machine. It has no moving parts! It is a surface with a slope, or incline. Inclined planes are used to change the height of an object. A common inclined plane is a ramp. Furniture movers use ramps because it takes less force to slide a heavy box up an inclined plane than to lift it straight up into a truck. It would take a certain amount of force to lift a box three meters. But if you use a ramp that is six meters long to raise the box three meters high, it takes only half the force! The longer the ramp and the gentler the slope, the less force is needed to move the load. But remember the trade-off. The gentler and longer the slope, the farther you have to push or pull the load.

斜面是一种非常简单的机器。 它没有活动部件!它是一个有坡度的曲面。 斜面用于改变物体的高度。 常见的斜面是斜坡。 家具搬运工使用斜坡，因为把一个沉重的箱子从斜面上滑上，比直接把它抬到卡车上所需的力要小。 把箱子抬三米需要一定的力。 但如果你用6米长的斜坡把盒子抬到3米高，只需要一半的力!斜坡越长，坡度越平缓，移动货物所需的力就越小。 但要记住权衡。 斜坡越平缓、越长，你就必须推或拉得越远。