Mon Prof Augmenté
Hollow hull and solid marble
Age 13 · Physics
A ship’s hull is mostly air-filled space, so the whole ship pushes aside more water than it weighs. A solid glass marble has no air inside it, so its density stays higher than water and it sinks.
This picture is part of the full library
Every lesson is open to everyone for 7 days after it is published. This one came out on September 23, 2026: its text stays readable here, and its picture opens with a subscription.
The app is free. A subscription opens every lesson, in every school year.
Age 13: open this week
Browse Age 13
In the picture
- Air chambers inside the hull: empty spaces that hold only air
- Steel hull plating: thin metal walls around the chambers
- Solid glass marble: no air inside, resting on the tank floor
- Water in the tank: the liquid the marble sinks through
Examples
- A steel cargo ship floats across the ocean.
- A glass marble dropped into a glass of water sinks to the bottom.
Key takeaways
- Average density is total mass divided by total volume, and trapped air adds volume without adding much mass.
- An object floats when its average density is less than the density of the water around it.
Quiz: Hollow hull and solid marble (Age 13)
-
What does the trapped air in a ship’s hull do to the ship’s average density?
-
How is average density calculated?
-
Why does a solid glass marble sink in water?
The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.
Free app, optional subscription
App Store Google Play
Carry on in the app
At least one new illustrated lesson every weekday for your child’s year, with its quiz and a reminder at 6:15 pm.
Your child’s teacher does not use My Enhanced Teacher yet?
Tell them about it
