62 Trucks and Diggers-Mid

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

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.

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.

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.

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.

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.