2
Bend and twist
Workbook 2: Topic 2.2, pp. 22–24
GoalSay that pushes and pulls can also bend and twist some objects.
New words
bend · to make something curved by pushing or pulling its endstwist · to turn the two ends of something in different waysflexible · able to bend without breaking
Explanation
A force can also bend an object. If you push the two ends of a paper strip towards each other, the strip bends into a curve. A force can twist an object too. If you hold a wet cloth and turn your hands in different ways, the cloth twists into a rope. A thick rope or a thin piece of wool can be twisted. Things that bend easily are flexible. Some things are stiff, so they do not bend easily. A ruler made of wood bends only a tiny bit before it might snap, so we do not push it too hard.
Worked examples
Omar pushes the two ends of a paper strip towards each other. The strip bends into a curve.
Aisha turns one end of a rope one way and the other end the other way. The rope twists.
A grown-up can bend a paperclip open with their fingers. A metal key is too stiff to bend by hand.
Class activity
Bend or twist? (with an adult): use things that are safe to handle: a paper strip, a long piece of wool, a tea towel and a pencil. Try to bend, then to twist each one. Do not force the pencil. Make a table with two columns, “bends” and “twists”, and tick it.
Practice
1
What can you do to a paper strip to make a curve?
Bend it. Push its two ends towards each other.
2
Tom turns the two ends of a scarf in different ways. What is he doing to it?
Twisting it.
3
Which one is flexible: a rope or a brick?
A, the rope. It bends easily.
4
Write the four ways a force can change the shape of an object.
Squash, stretch, bend and twist.