Question

Which of the following statements is true? The weight of a column of seawater 1 m2 in cross section and 10 m high is about 2.00×105 N. The weight of a column of seawater 1 m2 in cross section and 10 m high plus the weight of a column of air with the same cross section extending up to the top of the atmosphere is about 2.00×105 N. The weight of 1 m3 of seawater at 10 m below the surface of the ocean is about 2.00×105 N. The density of seawater is about 2.00×105 times the density of air at sea level.

Answer 1

“The weight of a column of seawater $1 \mathrm{m}^{2}$ in cross section and 10 m high + the weight of a column of air with the same cross-section elongating up to the top of the atmosphere is about $2.00 \times 10^{5} \mathrm{N}$” is true from the above-given sentences.

Explanation:

It depends on if you are talking about gauge pressure or total pressure. The “weight of a column” of seawater $1 \mathrm{m}^{2}$ in “cross section” and 10 m high is about $2.00 \times 10^{5} \mathrm{N}$. This is gauge pressure, which considers the surrounding air pressure, and only reads off pressure above “air pressure”. “The weight of a column of seawater $1 \mathrm{m}^{2}$ in cross section and 10 m high + the weight of a column of air with the same cross-section elongating up to the top of the atmosphere is about $2.00 \times 10^{5} \mathrm{N}$”. The “total pressure”, which considers the “pressure” of the whole which is above a certain height.