THE PHYSICAL EDITION
Clay and Cargo
Vince wants to give his stones a ride. He reshapes a sinking lump of clay, watches his boat settle lower as he adds stones, and finds a smaller-load plan after water comes in. A quiet story about shape, floating and trying again.
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A sinking lumpPages 1–2
Vince releases a solid clay lump into a shallow tub. It settles on the bottom while four stones wait on a blue cloth. The selected clay is denser than water. A solid lump sinks; the waiting stones give Vince a reason to try a different shape.
Ask together: What could Vince change about his clay?
A hollow hullPages 3–4
Vince presses the same clay wide and turns its edges up into a broad bowl. An intact hollow shape can keep water out of a larger space. The raised edges and unbroken bottom matter; a wide solid pancake is not the same thing.
Ask together: Where could water get into a boat?
Floating after releasePages 5–6
Vince lowers the empty clay bowl into the tub, then takes both hands away. It floats with a dry interior. The clay has not become lighter. A suitable bowl shape can displace enough water to support its weight before water reaches its rim.
Ask together: What changed, and what stayed the same?
Returning after releasePages 7–8
Vince gently presses the empty bowl a little deeper, then lifts his fingers away. The bowl rises while remaining partly in the water. A slightly deeper intact boat displaces more water. If it stays level, dry and undamaged, the increased upward force can lift it again after release.
Ask together: What happens when Vince lets go?
A lower ridePages 9–10
One stone rides in the dry hull. With three stones aboard, the same boat sits lower in the water. Added cargo increases the weight. A floating hull settles deeper until the upward force balances its new total weight, provided it can still keep water out.
Ask together: Which boat has more rim above the water?
Water over the rimPages 11–12
Vince adds the last stone. Water crosses the low rim and enters the clay bowl. A low open rim can let water in when a load brings it down to the surface. The exact load depends on the clay, hull and stones; these counts are illustrative.
Ask together: Where does the water enter?
Emptying and drainingPages 13–14
Vince removes the stones and tips water out of the intact bowl. The empty dry hull can float again. Removing the cargo alone does not empty a flooded boat. Vince drains the water before relaunching the undamaged hull.
Ask together: What two things does Vince take out?
Several tripsPages 15–16
Vince nudges a one-stone load across the tub, then lifts the stone out at the far blue cloth. Three stones still wait for later trips. A smaller load leaves more rim above water. Repeating a successful lighter trip gives Vince a way to carry the stones without trying to carry them all at once.
Ask together: How could the waiting stones get their rides?
Sources and evidence
The selected dense non-hardening modeling clay sinks as a compact solid lump in water.
ACS Grade 5 Lesson 2.4: Density and Sinking and Floating, Teacher Background
The clay is selected to be denser than water; not every modeling material behaves the same way.
The same clay can float when formed into a broad watertight bowl whose above-water rim keeps water out and whose submerged envelope excludes enough water.
ACS Grade 5 Lesson 2.4: Density and Sinking and Floating, Teacher Background
The bowl needs an intact watertight bottom and raised rim, enough space to displace water, and a dry interior. Reshaping does not reduce the clay mass.
An intact stable empty floating bowl depressed gently without flooding can rise after the fingers separate.
OpenStax University Physics Volume 1, 14.4 Archimedes’ Principle and Buoyancy
The gentle press is conditional on a level, unchanged, dry hull with its rim above water. Soft clay can deform, tip or flood.
Adding cargo makes the same stable boat float deeper while its dry interior excludes more water; removing cargo before flooding can reduce the required immersion.
OpenStax University Physics Volume 1, 14.4 Archimedes’ Principle and Buoyancy
One, three and four stones are an illustrative sequence, not a tested load limit. Hull thickness, shape and stone size change the result.
If loading brings the rim low enough for water to enter, an open dense clay hull can flood and sink.
OpenStax University Physics Volume 1, 14.4 Archimedes’ Principle and Buoyancy
Water entry must occur at a rim low enough to be overtopped. Upward force also acts on sinking objects; it is insufficient to support this flooded dense hull.
Emptying the water and cargo from an undamaged hull restores the light-load conditions; carrying smaller loads in several trips can solve the cargo task.
ACS Grade 5 Lesson 2.4: Density and Sinking and Floating, Teacher Background
Vince removes the cargo and drains an intact hull before relaunch. Draining does not repair cracks. The story shows the first delivery and proposes later trips.