Question

A barge filled high with sand approaches a low bridge over the river and cannot quite pass under it. Should sand be added to, or removed from, the barge? [Hint: Consider Archimedes’ principle.]

Short answer

Yes, the sand should be added to the barge.

Step-by-step solution

Understanding the motion of barge underwater

Due to buoyant force, the barge floats underwater. If the displaced water weight is less than or equal to the barge weight, the barge will float under the water.

Explain whether sand should be added or not.

If the sand is removed from the barge, it will not be capable of displacing more water. The barge will become lighter in weight. As the weight of the barge is less so it will rise under the water.

Then, it will come closer to the bridge. Due to this, the barge will not fit into the bridge, and it may slip under the bridge.

If the sand is added to the barge, the barge will eventually sink under the water and thus fit under the bridge. But the sand should be added in a specific amount not to lose the advantage of adding it.

Thus, sand should be added to the barge.