Idea 3of 8Builds onThe touching test
The pull along a rope
A lamp hangs from a cord. What is the cord doing?
Today you'll discover
- what a cord does to the lamp it holds
- which way a rope can ever act
- the name for a rope's pull
Think firstA lamp hangs still from a cord
The lamp hangs still. What is the cord doing to it?
Decide first, then press Next. Watch which way the cord's arrow runs.
A box with a dot at its centre hanging from a cord drawn up to a ceiling. After a prediction an arrow appears pointing straight down from the centre, then a second arrow of the same length pointing up along the cord. The cord's pull is then named. The last step asks what a tug-of-war rope does to each team.
See the whole ideathe big idea and the key word, in one place
The big idea
A rope pulls along its length. It never pushes.
Easy to get wrongA rope cannot push. Try to push a crate with a rope and it folds. Tension only ever points along the rope, toward its middle.
Key word
- tension
- the pull a stretched rope, cord or cable exerts along its length; symbol FT, the same all along a light rope
About this modelArrows are forces, not motion: a box can move with no arrow pointing its way.
Arrows are forces, not motion: a box can move with no arrow pointing its way.
Ready to use it?
- Find the direction of a rope's pull on a described object, and say what it matches when nothing moves.