3D Shapes – Solids That Take Up Space
Every shape you've studied so far in this course – circles, triangles, squares, polygons – has been 2D (two-dimensional): flat, with only length and width. A 3D shape, also called a solid, adds a third dimension – height, or depth – so it takes up real space, the way a physical object does rather than a drawing on paper.
This section moves from the flat world of area and perimeter into the physical world of solids: boxes, balls, cans, and more. Some 3D shapes, like cubes and pyramids, are built entirely from flat faces; others, like spheres and cylinders, include at least one curved surface. Telling these two families apart is the first skill you'll need before naming and measuring any solid.
2D vs. 3D
A 2D shape has only length and width and is flat. A 3D shape has length, width, and height (or depth), and takes up space.
A sphere (like a ball) takes up space in all three dimensions, so it is a 3D shape.
Real-Life Application
- Packaging: boxes, cans, and bottles are all everyday 3D shapes.
- Architecture: buildings are designed and built as 3D solids.
- 3D printing: printers build up physical solid objects layer by layer.
Key Takeaways
- 3D shapes (solids) have length, width, and height, and take up space.
- 2D shapes are flat, with only length and width.
- 3D shapes can be flat-faced (like a cube) or include curved surfaces (like a sphere).
Practice: 3D Shapes
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