Squash and Spring

For Grown-Ups Vince wants to make a bed for his toy duck. Follow his hands: what changes while they touch a material, and what happens when they move away? Each story spread shows successive moments. A shape that comes back A push can squash this sponge against the board. Bending it changes its shape another way. When Vince removes his hands, the resilient foam returns towards its earlier shape. This is elastic behaviour. Softness tells us how easily something yields; it does not tell us whether the new shape will remain. A shape that stays Soft modelling clay can keep a hollow after the pressing fingers leave. This is plastic deformation: the change is not automatically undone. Here, plastic describes a kind of shape change, not the name of the material. The clay has not turned hard. Vince can press it into a wider shape. Two useful behaviours The shaped clay makes the bed’s low sides. The foam supplies a yielding cushion. Neither material is best for every job. A light toy may barely compress its cushion; we do not need a large dent to know what Vince felt with his hand. Look together Find a hand touching the sponge, then a gap. Which shape returns? Which hollow remains? What does Vince change after he notices that the sponge will not stay bent? Try a gentle comparison With a grown-up, choose a clean resilient foam sponge and soft modelling clay suitable for the child. Press each gently against a tray, lift your hand away and watch. Try another gentle shape. Do they respond alike? Avoid mouths and tearing pieces off; follow the material’s age and handling guidance. Watching is welcome. Different materials, different responses Some foams recover slowly, lose shape or tear. Clay stiffness also varies. Use what your own materials show; do not force them to match the pictures. The story compares these two examples, not every sponge or every clay. No timing or equal-force measurement is shown. Science: Institute of Physics, Stretching and compressing materials; OpenStax, Elasticity: Stress and Strain; Polyurethane Foam Association, Foam Performance; Crayola, non-hardening modelling clay information.