Bring the ball back

1 · Watch the second pinch

Beginner

What happened every time the air pocket attached to the sphere pinched off a second time?

The sphere kept sinking and never came back The sphere rose faster to the surface The sphere stopped and hovered at mid-depth

2 · Apply the buoyancy rule

Rule from the article: the sphere returns only if the volume it displaces, counting its air and measured in sphere volumes, exceeds its density ratio.

Intermediate

A sphere 1.37 times as dense as water displaces, with its air, 1.30 times its own volume. What happens?

It keeps sinking It turns around and rises It floats at rest

3 · Weigh a heavy ball

Expert

A sphere 3.5 times as dense as water: how much displaced volume would it need to keep in order to rise?

About 1.5 sphere volumes More than 2.5 sphere volumes More than 3.5 sphere volumes

4 · Judge a threshold

Cavities that survived and cavities that broke generally fell on opposite sides of a reference neck radius, built from buoyancy, weight and surface tension.

Expert

Why do the authors refuse to treat this reference radius as a predictive threshold?

Because it was measured on too few spheres Because a closing neck crosses any threshold before it breaks Because surface tension plays no role at the neck

Ball recovered

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