Impact of Dropping Stones from a Floating Boat on Pond Water Level

When considering the phenomenon of dropping stones from a floating boat into a pond, it is interesting to understand the different effects on the water level. This article delves into the physics behind this process and explores how the water level changes at different stages.

Understanding Water Displacement

Water displacement refers to the volume of water that is pushed out of the way when an object is submerged in it. According to Archimedes' principle, any object immersed in a fluid will experience an upward force equal to the weight of the fluid that is displaced. This principle is crucial in understanding the changes in water level observed when stones are dropped from a floating boat.

Before Dropping the Stones

When the stones are on the floating boat, the boat's buoyancy is in balance with the total weight of the boat and the stones. The boat displaces a volume of water that is equivalent to the combined weight of the boat and the stones. As a result, the water level in the pond rises due to this displacement.

After Dropping the Stones

Once the stones are dropped into the water, they displace a volume of water equal to their own volume, not their weight. Since stones are generally much denser than water, the volume of water displaced when the stones are submerged is significantly less than the volume of water that was displaced when the stones were on the boat (based on their weight).

Conclusion

As a result of this process, the water level in the pond experiences a change:

Before Drop: The water level increases because the combined weight of the boat and stones displaces a larger volume of water. After Drop: The water level decreases when the stones are dropped, as they displace less water by volume than they did when on the boat.

The overall effect is a decrease in water level once the stones are dropped into the pond. This phenomenon is a direct consequence of the difference between the volume of water displaced by the stones based on weight and their volume when submerged.

Weight Comparison: Boat vs. Stones

It is essential to understand that while the stones themselves weigh more than the water they displace, the boat provides additional buoyancy. The displacement of water by the boat and stones together initially causes a rise in the water level. However, when the stones are dropped, they displace less water by volume, leading to a net decrease in water level.

The displacement of 1 kg per liter of water provides a quantitative basis for this observation. The weight of the stones displaces more water than their volume when they are on the boat, but they displace less when submerged. This reduction in displacement directly translates to a decrease in the water level.

Floating Rationale

For floating stones, the scenario remains similar. If the stones float, the volume displaced by the combined weight of the boat and stones is the same as before. However, if they sink, their total volume of displacement decreases, leading to a reduction in water level. The density of the stones plays a crucial role here. Since they are denser than water, they displace less water when submerged.

In summary, the water level in the pond will decrease when the stones are dropped into the water, due to their lower displacement when submerged compared to their weight-based displacement when on the boat.