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CBSE Class 2 · Mathematics

Shapes Around Us (3D Shapes)

Official NCERT chapter from Joyful Mathematics (English) (book code bejm1). ExamMaster notes are original teaching at CBSE Class 2 depth.

This lesson follows the official chapter “Shapes Around Us (3D Shapes)” in Joyful Mathematics (English). The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.

  • CBSE Class 2
  • Easy level
  • 8 concepts

1A drum and a matka share a rounded body

Both can roll on a curved side. That shared feel is the match, not the song the drum makes.

A square box does not share that rounded body even if it is painted like a drum.

Figure. A drum and a matka share a rounded body you can roll on a curved side. A square box does not share that feel, even if it is painted like a drum. Outlines here are stand-in blocks, not rounded drawings.

How it works

  1. Try a roll on the sideDrum, then matka.
  2. Ask if the feel matchesCurved body?
  3. Ignore the songSound is not the shape test.

2Match instruments that share a shape, not a song

Two instruments that both slide on a flat face share a shape-sort. A loud one and a quiet one do not.

Song peels off. The feel-test stays.

Figure. Match instruments that share a shape-sort, not a song. Drum and matka both pass the curved-side feel-test. Loud and quiet name volume, which peels off and does not sort the shape.

How it works

  1. Silence the songCover the name if you must.
  2. Run the feel-testRoll, slide, or stack.
  3. Match the testersSame motion, same pair.

3Cube, cuboid, cylinder, cone, sphere by feel

Those school names wait for a feel-test: faces, roll, point, every-way round.

Saying the name before the test is a label with no job.

Figure. School names wait for a feel-test: six faces, roll, a point, or every-way round. The boxes stand for the objects; a sphere is not drawn as a circle because that outline is not available.

How it works

  1. Pick one objectDie, tin, ball, cone cap.
  2. Run one feel-testFaces, roll, or point.
  3. Then pin the school nameCube, cuboid, cylinder, cone, sphere.

4Faces you can count on a box

A cuboid has faces you can rest it on. Count the rests, not the pictures printed on it.

A ball has no flat rest-face. Do not invent six faces for a sphere.

Figure. A cuboid has six rest-faces. Laid as a cross they stay joined: top, four side faces in a belt, and the base. Count the rests, not any picture printed on a face. A ball has no flat rest.

How it works

  1. Rest the boxOne face down.
  2. Turn to a new restA new face.
  3. Count the restsThat is the face-count.

5Edges and corners

An edge is where two faces meet. A corner is where edges meet. You can run a finger along an edge and stop at a corner.

A sphere has neither. A cone has a point that is a different kind of corner.

Figure. An edge is where two faces meet; a corner is where edges meet. This cabinet sketch of a box has twelve edges and eight corners. A sphere has neither. Depth is a sketch, not a measured solid.

How it works

  1. Find a face-meetingThat line is an edge.
  2. Find an edge-meetingThat point is a corner.
  3. Refuse them on a ballNo flat faces to meet.

6Roll, slide, or stack as a test

Roll needs a curve. Slide needs a flat face. Stack needs a face that can hold another object.

One object may pass more than one test. Name the test you ran.

Figure. Roll needs a curve, slide needs a flat face, and stack needs a face that can hold another object. Name the test you ran; one object may pass more than one.

How it works

  1. Try rollDoes it go every way, or on a side?
  2. Try slideA flat path.
  3. Try stackWill another object rest on it?

7A net is the skin unfolded

A net is the faces laid flat, still joined as they were. It is not a new object.

If the faces would not fold back into the box, it is not that box’s net.

Figure. A net is the skin unfolded: the same six faces, still joined along the edges that will fold. Dashed joins are those fold edges. If the faces would not close back into the box, the drawing is not that box's net.

How it works

  1. Imagine cutting an edgeOpen the box like a skin.
  2. Lay the faces flatStill joined.
  3. Ask if it folds backIf not, wrong net.

8Same shape, different size is still that shape

A small ball and a big ball share the every-way round test. Size is not the sort.

A small box is still a cuboid. Do not rename it because it is cute.

Figure. A small cuboid and a large cuboid share the six-face test. The large box is drawn twice as wide and twice as tall as the small one. Size is not the sort: both stay cuboids.

How it works

  1. Run the same feel-testOn both sizes.
  2. If the test matchesSame school name.
  3. Leave size as sizeNot a new shape.
A drum and a matka match when they share
  1. A rounded body you can feel
  2. The same song
  3. The same colour

The feel-test is the match.

Notes

  • The official chapter title is “Shapes Around Us (3D Shapes)”. Teach the school test for that title, not a contest shortcut.
  • If a step needs a later class, stop. The next official chapter will pick it up.

Recap

Hold these pegs from the official chapter “Shapes Around Us (3D Shapes)”. The wording is ExamMaster’s teaching, not a textbook recap.

A drum and a matka share a rounded body
Both can roll on a curved side. That shared feel is the match, not the song the drum makes.
Match instruments that share a shape, not a song
Two instruments that both slide on a flat face share a shape-sort.
Cube, cuboid, cylinder, cone, sphere by feel
Those school names wait for a feel-test: faces, roll, point, every-way round.
Faces you can count on a box
A cuboid has faces you can rest it on. Count the rests, not the pictures printed on it.
Edges and corners
An edge is where two faces meet. A corner is where edges meet. You can run a finger along an edge and stop at a corner.
Roll, slide, or stack as a test
Roll needs a curve. Slide needs a flat face. Stack needs a face that can hold another object.

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