# Can you solve the boat puzzle? | Summary and Q&A

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October 27, 2015
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Physics Girl
Can you solve the boat puzzle?

## TL;DR

When a rock is thrown into the water from a boat, the water level will go down.

## Key Insights

• π¦ Displacement of water is the key factor in determining the change in water level when objects are submerged.
• π¦ Archimedes' principle helps explain why the water level does not change when a rock is thrown into the water from a boat.
• πΌ Extreme cases can be used to simplify and understand complex concepts.
• ποΈ Extreme cases help build intuition and provide a grounding in reality.
• π Empirical rules, like Archimedes' principle, may not always be intuitive.
• π€½ A lightweight boat will have a minimal effect on the water level when a person jumps into the water.
• π¦ Understanding the balance between weight, displacement, and buoyant force is crucial in analyzing water level changes.

## Transcript

Imagine that you're sitting on a boat, floating in the water, and holding a rock that you then throw into the water, and it sinks. Did you just cause the water level to rise, fall, or stay the same? I want you to think on that for a minute. And to make the problem a little more clear, imagine the boat is in a container not much bigger than the boat... Read More

### Q: Does the water level change when a rock is thrown into the water from a boat?

No, the water level stays the same. This is because the weight of the rock was already displacing the water when it was in the boat.

### Q: What is Archimedes' principle?

Archimedes' principle states that the buoyant force on an object submerged in water is equal to the weight of the volume of water that object displaces.

### Q: How can extreme cases help understand the concept better?

Extreme cases, such as using a super heavy but small rock, can simplify the problem and provide a visual understanding of the concept. In extreme cases, it is clearer to see how the displacement of water affects the water level.

### Q: What happens to the water level when a person jumps into the water from a boat?

The water level stays the same. Archimedes' principle applies in this case as well, where the weight of the person and the boat combined is equal to the weight of the water displaced.

## Summary & Key Takeaways

• When a rock is thrown into the water from a boat, the water level stays the same because the displacement of the rock's weight is already accounted for by the boat.

• Archimedes' principle states that the buoyant force on an object submerged in water is equal to the weight of the volume of water that object displaces.

• Extreme cases, such as using a super heavy but small rock, can help understand the concept better.