Pressure · 压强
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| pressure/ˈpreʃə/ | 压强 | yā qiáng |
| pascal/ˈpæskl/ | 帕斯卡 | pà sī kǎ |
Snowshoes float you; stilettos sink in
- Step onto soft snow in boots and you sink; strap on snowshoes and you walk on top.
- Same weight, spread over a bigger area — so the pressure 压强 is much smaller.
- Pressure is force spread over area, and it rules everything about fluids.
- Deep in the ocean it crushes; under a sharp blade it cuts.
雪鞋让你浮着;高跟鞋却陷进去
- 穿靴子踩上松软的雪你会陷下去;绑上雪鞋你就能在上面行走。
- 同样的重量,摊在更大的面积上——所以压强小得多。
- 压强是力摊在面积上,它主宰着流体的一切。
- 在深海它会压碎你;在锋利的刀刃下它能切割。
Defining pressure
- Pressure is force per unit area: $P = \dfrac{F}{A}$.
- Its unit is the pascal 帕斯卡 ($1\ \text{Pa} = 1\ \tfrac{\text{N}}{\text{m}^2}$).
- The same force over a smaller area gives a larger pressure — hence sharp knives and needles.
- Spread the force out (snowshoes, wide tyres) and the pressure drops.
压强的定义
- 压强是单位面积上的力:$P = \dfrac{F}{A}$。
- 它的单位是帕斯卡($1\ \text{Pa} = 1\ \tfrac{\text{N}}{\text{m}^2}$)。
- 同样的力作用在更小的面积上给出更大的压强——因此有锋利的刀和针。
- 把力摊开(雪鞋、宽轮胎),压强就下降。
A force of $200\ \text{N}$ presses on an area of $0.5\ \text{m}^2$. What is the pressure, in $\text{Pa}$? · 大小为$200\ \text{N}$的力作用在面积为$0.5\ \text{m}^2$的表面上。压强是多少$\text{Pa}$？
$P = F/A = 200/0.5 = 400\ \text{Pa}$.
The same force on a smaller · 较小 area produces: · 相同的力作用在更小的面积上会产生：
$P = F/A$: a smaller area gives a larger pressure — why knives and needles are sharp. · $P = F/A$：面积越小，压强越大——这就是刀和针要做得尖锐的原因。
Pressure is measured in ____ (the SI unit). · 压强的测量单位是____（国际单位制单位）。
$1\ \text{Pa} = 1\ \tfrac{\text{N}}{\text{m}^2}$.
Pressure in a fluid grows with depth
- In a fluid, pressure increases with depth: $P = \rho g h$.
- Deeper down, more fluid weighs on you, so the pressure is greater.
- It depends on depth $h$ and density $\rho$ — not on the container's shape.
- This is why dam walls are built thick at the bottom, where pressure is highest.
流体中的压强随深度增大
- 在流体中,压强随深度增大:$P = \rho g h$。
- 越深,压在你身上的流体越多,所以压强越大。
- 它取决于深度 $h$ 和密度 $\rho$——不取决于容器的形状。
- 这就是为什么大坝墙在底部建得厚,那里压强最高。
Find the water pressure $2\ \text{m}$ deep ($\rho = 1000\ \tfrac{\text{kg}}{\text{m}^3}$, $g = 10\ \tfrac{\text{m}}{\text{s}^2}$), in $\text{Pa}$. · 计算深度为$2\ \text{m}$处的水压（$\rho = 1000\ \tfrac{\text{kg}}{\text{m}^3}$, $g = 10\ \tfrac{\text{m}}{\text{s}^2}$），结果单位为$\text{Pa}$。
$P = \rho g h = 1000 \times 10 \times 2 = 20\,000\ \text{Pa}$.
Fluid pressure pushes every way
- At any point in a fluid, the pressure pushes equally in all directions.
- It acts on every surface it touches, always perpendicular to that surface.
- This is why a submarine is squeezed from all sides, not just the top.
- The all-directions rule is what makes hydraulics and buoyancy work.
流体压强向各个方向推
- 在流体中的任一点,压强向各个方向等量地推。
- 它作用在它接触的每个表面上,始终垂直于该表面。
- 这就是为什么潜艇是从四面八方被挤压,而不只是从顶部。
- 正是这个"各个方向"规则让液压和浮力起作用。
Pressure with depth · 压强与深度
In a fluid, the pressure rises steadily with depth below the surface. · 在流体中，压强随表面以下的深度增加而稳定增大。
At the same depth, a narrow tube and a wide lake have the same fluid pressure. · 在同一深度，细管和大湖中的流体压强相同。
Fluid pressure depends only on depth and density ($P = \rho g h$), not the container's shape. · 流体压强仅取决于深度和密度（$P = \rho g h$），与容器形状无关。
Select all · 所有 true statements about fluid pressure. · 选择所有关于流体压强的正确陈述。
Fluid pressure grows with depth and density and pushes all ways — but does not depend on the container's shape. · 流体压强随深度和密度增加并向各个方向推挤，但不取决于容器的形状。
Fluid pressure depends on depth, not on the amount of fluid or the container's shape. A thin tall tube and a wide lake of the same depth have the same pressure at the bottom. And pressure pushes in all directions, not just downward.
流体压强取决于深度,而非流体的量或容器的形状。同样深度的细高管和宽阔的湖,底部压强相同。而且压强向各个方向推,不只是向下。
Find the water pressure $2\ \text{m}$ below the surface ($\rho = 1000\ \tfrac{\text{kg}}{\text{m}^3}$, $g = 10\ \tfrac{\text{m}}{\text{s}^2}$).
- $P = \rho g h = 1000 \times 10 \times 2 = 20\,000\ \text{Pa}$.
That is the extra pressure from the water alone, on top of the air pressure above.
求水面下 $2\ \text{m}$ 处的水压($\rho = 1000\ \tfrac{\text{kg}}{\text{m}^3}$,$g = 10\ \tfrac{\text{m}}{\text{s}^2}$)。
- $P = \rho g h = 1000 \times 10 \times 2 = 20\,000\ \text{Pa}$。
那是仅来自水的额外压强,叠加在上方的空气压强之上。
Pressure is force per unit area, $P = \dfrac{F}{A}$ (in pascals). A smaller area gives more pressure. In a fluid, pressure grows with depth as $P = \rho g h$ — set by depth and density, not the container's shape — and pushes equally in all directions.
压强是单位面积上的力,$P = \dfrac{F}{A}$(单位帕斯卡)。更小的面积给出更大的压强。在流体中,压强随深度增大为 $P = \rho g h$——由深度和密度决定,而非容器形状——并向各个方向等量地推。