Book 3, Question 13 · Video
Why Do Submarines Sink and Rise?
A submarine has special ballast tanks. Fill them with water, and the craft gets heavier and sinks. Blow the water out with air, and it gets lighter and rises!
Read the full answer →What Crafty Clover says in this video
Intro
Hey there, curious minds! I'm Crafty Clover! Let's discover something amazing. Why do submarines sink and rise?
The Big Idea
A submarine has special ballast tanks. Fill them with water, and the craft gets heavier and sinks. Blow the water out with air, and it gets lighter and rises! It is like a big underwater elevator.
Step 1
Step one: on the surface. Floating is a contest between weight and the water's upward push. On the surface, the submarine is light enough that the water's push wins, so it floats. It is just like a boat, only much bigger and much safer.
Step 2
Step two: the tanks fill, and the sub sinks. Valves open, and water rushes into the ballast tanks. Now the submarine is heavier than the water's push, so it sinks. Crew members control which tanks fill and which tanks empty.
Step 3
Step three: air goes in, and the sub rises. To come back up, the crew blows air into the tanks. The air pushes the water out, the sub gets lighter, and it rises to the top. Then the submarine can stay high, or low, or somewhere in the middle.
A Closer Look
Let's take a closer look at a submarine! When a tank holds water, the sub is heavy. When a tank holds air, the sub is light. And tiny fins help the sub aim up or down. Water down, air up! It is a clever mix of weight, air, and water.
Quick Facts
Quick facts! Those special tanks are called ballast tanks. Submarines also use tiny fins to aim. Fish use a built-in air bag called a swim bladder for a similar trick. And divers wear a vest that they can puff up or let down to hover in the water. Each animal or machine uses air to change how it floats.
Think Like a Scientist
Now, think like a scientist! First, a closed empty bottle floats in a tub. Next, add some water, and it sinks. Never try this in a pool without a grown-up. Always keep a grown-up nearby. That is a great way to see ballast at work.
Outro
Change the weight, and you change who wins. That's how submarines sink and rise! Crafty Clover can be found on Amazon Books, Google Bookstore, and Apple Books. Available for purchase or download! Bye for now!