A Swimming Pool Problem
A curious college physics student places a row boat
in a swimming pool, loads the boat with a number of bricks, and
rows to the center of the pool. Once there, the student carefully
notes the water level, throws the bricks into the swimming pool
and once again notes the water level. Eureka !! the student exclaims,
I was right. What had happened to the water level in the pool?
- A. Nothing, the water level did not change.
- B. The water level increased due to the bricks thrown into
the pool.
- C. The water level became lower.
- D. I can't swim, and don't even like water (or bricks).
Answer
A Swimming Pool Problem - Answer = C
While the bricks are in the boat, the buoyant force supports the
boat, student, and bricks. When the bricks are thrown into the
water and sink to the bottom of the pool, the buoyant force supports
mainly the boat and student, since the bricks are now supported
by the bottom of the pool. (There is a small buoyant force on
the brick due to the volume of water they displace, but it small
compared to the weight of the bricks.) Since the buoyant force
supports less weight with the bricks in the pool, less volume
of water is displaced, and the pool water level decreases.
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| UW-Stout Physics Department |
