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Students learn about three-dimensional shapes and find them in the world around them.
Have you ever noticed that a drawing of a pizza is flat, but a real pizza box is something you can actually pick up and open?
In the world of math, we talk about two kinds of shapes. 2D shapes are flat, like a drawing on a piece of paper. 3D shapes are 'solid.' This means they take up space and you can hold them in your hand! While a flat square has only length and width, a 3D shape also has height. Think of a circle on a page versus a basketball you can bounce. Because they are solid, 3D shapes have different parts we can feel, like smooth curved sides or straight flat faces.
Quick Check
If you can pick an object up and hold it in your hand, is it 2D or 3D?
Answer
It is a 3D shape.
There are four main 3D shapes we see every day. First is the sphere, which is perfectly round like a marble. Second is the cube, which looks like a box with 6 square sides. Third is the cylinder, which is long and round like a tube or a can of soup. Finally, there is the cone, which has a flat circle on the bottom and comes to a sharp point at the top, just like an ice cream cone!
Let's look at items in a kitchen to find our shapes: 1. A sphere is like an orange. 2. A cube is like a box of tissues. 3. A cylinder is like a tall glass of milk. 4. A cone is like a party hat for a birthday!
Quick Check
Which 3D shape looks like a dice used in a board game?
Answer
A cube.
Because 3D shapes have different surfaces, they move in different ways. Shapes with curved surfaces, like the sphere, love to roll! Shapes with flat faces, like the cube, are great at sliding. Some shapes are extra special! A cylinder has both. It has flat circles on the ends so it can slide, but a curved middle so it can roll if you lay it on its side. Understanding if a shape is flat or curved helps us predict how it will move.
Imagine you are at the top of a slide with three objects. Which will reach the bottom first? 1. A sphere (ball): It will roll very fast because it is all curved. 2. A cube (block): It will slide down slowly because it has flat faces. 3. A cylinder (glue stick): If you stand it up, it slides. If you lay it down, it rolls!
If you want to build a tall tower that doesn't fall, which shapes should you use? 1. Use cubes for the bottom because their flat faces stack easily. 2. You can put a cylinder on top of a cube. 3. Do NOT put a sphere in the middle, or the tower will roll away! 4. A cone is a great 'roof' for the very top.
Which shape is perfectly round and has no flat faces?
How many flat square faces does a cube have?
A cylinder can both roll and slide.
Review Tomorrow
In 24 hours, look around your room and try to find one object for each shape: a cube, a sphere, a cylinder, and a cone.
Practice Activity
Try this on your own: Take a soup can (cylinder) and a box (cube). Try to stack the box on the can, then try to stack the can on the box. Which way is easier?