62 Trucks and Diggers-Mid

Trucks and Diggers FOCUS Question How do trucks and diggers do work?

卡车和挖掘机焦点问题卡车和挖掘机是如何工作的?

Made for Work People use trucks to move heavy things. People use diggers to make holes in the ground. Trucks and diggers are big machines. They help people do work. In science, work means using a force to make something move. A force is a push or a pull.

人们使用卡车来搬运重物。 人们用挖掘机在地上挖洞。 卡车和挖掘机都是大机器。 他们帮助人们做工作。在科学中，做功意味着用一种力使某物运动。 力是推或拉。

Backhoe A backhoe is a kind of digger. It pulls up dirt with its bucket. Pulling on a load is work. Then it moves the dirt to a new place. Moving a load is also work. Sometimes the bucket stops moving. The bucket just holds the dirt. The load is not moving so this is not work.

反铲挖掘机是一种挖掘机。 它用水桶把土拉上来。 拉重物是工作。 然后它把泥土移到一个新的地方。 搬运货物也是一种工作。 有时桶会停止移动。 水桶只装泥土。 负载没有移动，所以这不是功。

Dump Truck A digger fills the bed of a dump truck with dirt. The truck is holding a heavy load. But it is not doing work. It is not moving the load. Then a driver starts the truck. The wheels go around and push the truck to a new place. Now the dump truck is doing work.

一名挖掘机正在用泥土填满一辆自卸卡车的底盘。 卡车装载着很重的货物。 但是它没有做功。它没有移动负载。 然后司机发动了卡车。 轮子转动，把卡车推到一个新的地方。 现在自卸卡车开始工作了。

The bed of the dump truck has a machine called a lift. The lift pushes up the bed and the dirt. The truck is doing work. Once the bed is high enough, the dirt slides down The dump truck is not doing work. It is not pushing or pulling the dirt.

自卸卡车的底盘上有一台叫做升降机的机器。 电梯把床和泥土推上去。 卡车在做功。一旦堆得足够高，泥土就会滑下来。 它不是推或拉泥土。

Bulldozer A bulldozer pushes big piles of dirt or rocks. It moves loads that are too heavy for people to move The bulldozer moves. the dirt to a new place. It is doing work. Do You Know? If a bulldozer pushes the same load a longer way, it does more work.

推土机推着大堆的泥土或岩石。 它可以移动人们无法移动的重物。 把泥土搬到一个新的地方。它在做功。 你知道吗?如果一台推土机把同样的负荷推得更远，它做的功就更多。