Question

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Humpback whales mainly feed on krill, or shrimp-like crustaceans that live in the ocean. When humpback whales feed, they swim upwards with their mouths wide open and swallow thousands of krill all at once. The excess water that they swallow drains out through grooves in the whale's mouth.

According to the law of conservation of mass, what will the final mass of the whale be after it swallows the krill?
A.
It will equal the initial mass of the whale only.
B.
It will equal the initial mass of the whale plus the mass of the krill.
C.
It will equal the initial mass of the whale minus the mass of the krill.
D.
It will equal the initial mass of the krill only.

Answer 1

B.

By conservation of mass, the whale's mass after feeding equals its initial mass plus the mass of the krill it swallowed. The excess water drains out, so only the krill's mass is added.