Look at this piece of string and this lolly stick. Which one do you think can push? Which one can only pull? Hands up your guess — we will test it in a moment.

Today we will meet three engineering words: tie, strut and A-frame. You will feel what they mean when you build. First, though, we need to find out what string can do and what a stick can do.

In your group, try four quick tests. Hold both ends of the string and try to push a light book, then pull the book toward you. Do the same with a lolly stick: push, then pull. Talk about what each one can do. You will write it down later. For now, just notice and agree as a group. You may jot a two-word note if you need it.

Build a simple A-frame: join two lolly sticks at the top, then tie string across the bottom so the whole shape looks like the letter A. Stand it up and press gently on the top. Feel which part goes tight (that is the tie) and which parts get squashed and push down and out (those are the struts).

Record on your Investigation Journal page:

• what string can do and what a stick can do
• which material can only be a tie
• on your A-frame, which part was the tie, which parts were the struts, and how you could tell