Understanding Weight Displacement: The Bucket and Fish Experiment

Explore the fascinating world of physics with the classic bucket and fish experiment. Will adding fish to a bucket of water make it weigh 10 pounds more? This article delves into the principles of weight displacement, Archimedes' principle, and specific gravity to uncover the truth behind this seemingly simple scenario.

Does a Bucket of Water Weigh 10 Lbs Heavier if You Put Two 5 Lb Fish in the Water?

Contrary to what some might think, the addition of a 10-pound object, such as two 5-pound fish, does not necessarily increase the weight of the bucket by exactly 10 pounds. This is a common misconception that can be deeply satisfying to unravel with a bit of scientific understanding.

Let's break it down step-by-step. A bucket initially filled with water will have a certain weight, say 20 pounds. Adding 10 pounds of something (in this case, fish) means that the total weight of the bucket increases by 10 pounds, making it 30 pounds. For an unassuming observer, this might seem straightforward, but there's more to it than meets the eye.

Archimedes' Principle of Displacement

According to Archimedes' principle, any object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced by the object. This principle is what governs the behavior of objects in water and helps explain why a 5-pound fish displaces its weight in water.

When you add a fish to the bucket, the fish displaces an amount of water equal to its own weight. Consequently, the total weight of the bucket and the water increases by the weight of the fish. However, the weight of the water itself remains the same. It's as if the fish has pushed a similar weight of water out of the way, and that displaced water is now causing the bucket to weigh more.

The Impact of Specific Gravity

The specific gravity of the objects you're placing in the bucket also plays a role. If the fish were made of a material with a lower density than water, they would displace less water, and hence the increase in the bucket's weight would be less than 10 pounds. Conversely, if the fish were denser than water, they might displace more water than their weight, causing the bucket to weigh even more.

Practical Examples and Real-World Applications

This concept has practical applications in fields such as marine biology, where the density of different fish species affects their behavior in the water. It also has implications in engineering and design, where the displacement of fluids is critical for the functionality of many devices, such as submarines and ships.

Conclusion

So, does a bucket of water weigh 10 pounds heavier if you put two 5-pound fish in it? Yes, in a straightforward sense, it does. The true weight displacement happens through the displacement of water by the fish, not by a simple addition of weight. But remember, the true story often lies in the details and the principles that govern our physical world.