![]() The rate of kinetic energy transfer depends on (1) the number of particles and (2) how much kinetic energy they already have. Temperature is another measure, though observed through different measurements. ![]() Pressure is one measure of kinetic energy transfer from moving particles to a surface that they collide with. I once taught myself compute programming and made a particle-geometry collision simulator to test the following, and it seemed to work, so I'm drawing on the intuition that I learned from that project. I'll try to explain using molecular motion. Here's a perspective from a former chemistry student. Which gives us for the pressure $P_1$ and the velocity $v_2$: Let's assume the hose is completely horizontal so that Bernoulli's equation for comparing the fluid inside the hose ( $1$) and just outside the restriction ( $2$) is (expressing pressures as gauge pressures) ![]() (and somehow pressure decreases.) but when the finger blocks the hole, wouldn't that add extra pressure on the fluid? Like the garden hose ex: if you cover the hose with your finger, water flows out of the hose faster. This is just like if I pushed on a block with $5\,\rm N$ of force and you pushing on the block in the opposite direction with $10\,\rm N$ of force: the block would accelerate away from you and towards me, thus speeding up towards where the smaller force is being applied. This makes sense: if the pressure is higher on the left than on the right, then the fluid will speed up to the right. What Bernoulli's equation actually says is that the velocity will increase in the direction of decreasing pressure: $P_2-P_1=-\frac12\rho(v_2^2-v_1^2)$. This is a classic misunderstanding of Bernoulli's equation. I just can't wrap my head around why pressure decreases as velocity increases
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