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Summaries · Grade 4 Natural Sciences › Frame structures
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Frame structures

How frame structures are built, why triangles help, and where you find frames around you. Read one part at a time and tap “I know this”. Then test yourself in the quiz.

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What is a frame?

A frame structure is a ‘skeleton’ of bars (struts) joined together. Its job is to support and hold up a load. A solid clay brick is not a frame.

Square: wobbles and foldsWith a brace: two triangles, rigid
Add a diagonal straw, and the square stops wobbling.
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Build a strong frame

  • Join straws or sticks with tape, string or Prestik.
  • Use triangles and firm joints so the tower can carry more weight.
  • Put the legs of a tall tower wider apart at the bottom: a wide base is stable.
  • Test: add small masses one at a time on top.
Rule

A frame that does not bend or change shape is rigid.

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Frames in real life

  • Builders put cross-braces between the legs of a water-tank stand so it does not sway.
  • A roof truss holds up the roof.
  • A climbing frame on the playground must be strong, stable and safe.
  • A tent’s poles form a frame structure; an egg is a shell structure.
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Indigenous frame structures

Long before there were brick houses, people in South Africa built homes with a frame of struts, such as flexible branches, and covered it with grass, reeds or mats.

StructureHow it is built
Zulu beehive hut (iQhugwane)Bent branches form a dome frame that is covered with grass
Xhosa rondavelRound walls of poles and sticks plastered with mud (or mud bricks), under a cone-shaped thatched roof held up by a frame of poles
Nama matjieshuisBent sticks covered with woven reed mats; easy to take down and move

Other frame structures around us: roof trusses, bridges, cranes, pylons, and even your skeleton: your limb bones are struts.

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Remember this and test yourself

Remember this: your summary
  • A frame structure supports a load; its parts are called struts.
  • Frames around you: a pylon, a bed frame, a car’s chassis, a roof truss, a climbing frame.
  • Natural frames: a skeleton, the rib cage, a spider web, a bird’s nest.
  • A diagonal strut makes a wobbly square rigid; triangles are strong but light.
  • The weakest point of a frame is usually at the joints.

Write these points in your book. Read them again the night before the test.

Memory trick

Does it wobble? Give it a diagonal strut: one line turns one square into two strong triangles.

Flash cards · Tap to turn over

Important words

First say what the word means, then turn the card over.

Test yourself · Part 2

True or false?

Read the question and the answer. Is the answer right? Tap True or False.

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