Water and Wind

Wind moves the pinwheel. Wind is moving air. Vince feels it on his cheek and sees it push the pinwheel's angled blades.

Ask together: What tells you that the air is moving?

Water passes the rock. A leaf circles behind it. Most water passes the rock; some circles back in an eddy. Laminar flow is orderly; turbulence is irregular, mixing motion. A swirl alone cannot distinguish them.

Ask together: How does the leaf move compared with the water passing the rock?

Waves spread from the stream. The duck bobs. The falling stream makes waves that carry energy outward and make the toys bob. The stream's current also carries toys along. Bobbing and drifting are different motions.

Ask together: What moves up and down? What moves along the pond?

A duck floats. A pebble sinks. Water pushes upward on both objects. This buoyancy balances the duck's weight, but not the pebble's. The pebble's splash makes the rings on the next spread.

Ask together: Where is each object compared with the surface?

Two wave patterns approach one another. When gentle waves overlap, their heights add, briefly raising or lowering the surface. This interference does not erase the waves; they continue through one another.

Ask together: What might happen where the two patterns meet?

Tiny dents appear beneath the strider’s legs. Surface tension helps support the strider where its water-repellent legs dent the water. The duck floats mainly by displacing water.

Ask together: What do you notice where its legs meet the water?

The duck bubbles, fills and squirts. Squeeze underwater: air bubbles out. Release with the opening submerged: the elastic duck springs back, lowering pressure inside. The surrounding water pressure pushes water in. Squeeze above water: water exits through that same opening.

Ask together: What changes when Vince squeezes and then lets go?

A paper plane glides forward and down. The throw starts the plane moving. Airflow around its wings produces lift and turns air downward. Gravity pulls down; drag resists motion. In still air, the plane glides forward and gradually descends.

Ask together: Where might the plane go next?

Milk runs. Honey stretches into a thread. Honey's greater viscosity means greater resistance to flow. It makes a slow thread while milk runs readily. Temperature and pouring method also matter; this snack is an observation, not a controlled test.

Ask together: How do the milk and honey move differently?

Foam curves inward toward the drain. Gravity drives water through the drain. Existing turning motion can become a curved inward flow, traced by foam. Here water travels to the outlet, unlike waves crossing the pond. Not every drain swirls.

Ask together: Can you follow the foam toward the drain?

Vince sketches what he noticed. Vince records something he noticed. Drawings, marks or words let him return to an observation. He does not need all the answers.

Ask together: Which earlier picture matches one of his drawings?