Grades K–2

Why does a wagon need more than good wheels?

A toy wagon moves when someone pushes it. As its wheels turn, a new part of each wheel meets the ground. Rolling lets the wagon move without dragging its whole bottom along the path.

In the diagramWhat helps a wagon roll?WagonLevel pathPushWheels can turnPush, turning wheels, rolling right.

The wagon’s wheels roll on a surface. A route also needs a joined path.

The ground must still support those wheels. Track pieces that meet make a path from one place to the next. A large gap takes that support away. Good wheels cannot fill the missing piece.

A joined track makes a trip possible, but it does not choose the stops. Instructions such as “Go to the star, then to B” give that order. A push supplies movement, the track provides a route, and the words guide the person moving the wagon. These different parts work together.

Where these ideas lead

How do wheels help a wagon roll?
Wheels let the wagon roll along a surface.
How do track pieces make a route?
Joined pieces make a continuous path for that wagon.
How do exact instructions guide a character?
Instructions describe what the character should do on a usable path.

Illustrations simplify the real processes; any invented quantities or records are identified in the text.

Sources

Next Generation Science Standards — K.Forces and Interactions: Pushes and Pulls — grade-placement context
OpenStax — Simple Machines — adult background for rolling and ramps
OpenStax — 11.1 Rolling Motion
LEGO Education — Train Time
NGSS / National Science Teaching Association — K-2-ETS1-2 Engineering Design
CS Unplugged, University of Canterbury — Kidbots

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