78 Simple and Complex Machines-Mid

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 loosen the lid of a jar? You probably use tools. Tools 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. A hammer is a simple machine. Some machines combine several simple machines. Clocks and bicycles are complex machines. In this book, you will learn how machines make work easier.

你是怎么工作的? 你如何吃麦片或打开罐子的盖子? 你可能会使用工具。工具使工作更容易做。 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。 锤子是一种简单的机器。 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，你将了解到机器如何使工作更容易。

Do You Know? Animals use tools, too! Apes use sticks to get ants out of anthills. Sea otters use rocks to crack open clamshells. Crows can make wire hooks to get food out of a tall, thin container. What do we mean by work? In science, work means moving something. To move something you use force. The more force it takes to move an object, the more work is done. The more distance something moves, the more work is done. Whenever you push, pull, turn, or lift an object, you use force. The amount of force it takes depends on how heavy the object is. It takes a lot more force to move a big rock than to move a small rock.

你知道吗?动物也使用工具!猿用棍子把蚂蚁赶出蚁丘。 海獭用石头敲开蛤壳。 乌鸦可以用铁丝钩从又高又薄的容器里取出食物。 功是什么意思?在科学中，功意味着移动某物。 用武力移动某物。 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，做的功就越大。 无论何时你推、拉、转或举起一个物体，你都在使用武力。 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。

Machines make work easier by reducing the amount of force it takes to move an object, or load. But there is a trade-off. Machines make your work easier, but you have to work over a longer distance.

机器通过减少移动物体或负载所需的力来简化工作。 但这是一种权衡。机器使你的工作更容易，但你必须在更远的距离上工作。

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

简单机器的种类只有几种。 有些没有活动部件。 以下是你将在这本书中读到的7种简单的机器。

Inclined Plane The inclined plane is a very simple machine. It is a surface with a slope, or incline. Inclined planes help us change the height of heavy objects. A common inclined plane is a ramp. Furniture movers use ramps. It is easier to slide a heavy box up a ramp than it is to lift the box straight up. Moving the box up the slope of a ramp takes less force. The longer the ramp is and the gentler its slope, the less force it takes to move a box up it. 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。 它是一个有坡度的曲面。 斜面帮助我们改变重物的高度。 常见的斜面是斜坡。 家具搬运工使用坡道。 把一个沉重的箱子滑上斜坡要比直接把箱子抬起来容易得多。 把箱子移到斜坡上需要较少的力。 斜坡越长，坡度越平缓，搬运箱子所需的力就越小。 但要记住权衡。 斜坡越平缓、越长，你就必须推或拉得越远。