Thermodynamics Particles in Water

AI Thread Summary
The discussion revolves around calculating the number of fine metal particles in a water column at a height 1.0 mm above a reference point, given their thermal equilibrium and density. The participant initially considers using equations for internal energy and gravitational potential energy but realizes that internal energy remains constant across the two heights. They conclude that only the potential energy difference needs to be considered for the calculation. The relevant equation for potential energy, E = mgh, is identified as the key to solving the problem. The focus is on determining how the change in height affects the particle count in the specified volume.
dcrisci
Messages
45
Reaction score
0

Homework Statement


A column of water contains fine metal particles of radius 20 nm, which are in thermal equilibrium at 25°C. If there are 1000 such particles per unit volume at a given height h0 in the water column, how many particles would be found in the same volume 1.0 mm higher than h0? The density of the used metal is ρ = 20.0 g/cm3.

Homework Equations


## U = \frac{3}{2} nRT ##
## N = N_0 e^{\frac{E}{kT}} ##

The Attempt at a Solution


I am unsure of where to begin here, I just provided equations I though were necessary but am not exactly sure if they are the right ones. Any help to begin these problems would be awesome!

I was thinking of finding the internal energy of the water, and the difference in the gravitational potential energy of the particles 1mm higher, and then the total energy would be the sum of these two, which would be the value for E, then T = 298K N0 is 1000?
 
Physics news on Phys.org
dcrisci said:
I was thinking of finding the internal energy of the water, and the difference in the gravitational potential energy of the particles 1mm higher, and then the total energy would be the sum of these two, which would be the value for E, then T = 298K N0 is 1000?

Just realized that the internal energy would be equal at both volumes of water (height h0 and 1mm higher) so I could neglect this and only use the potential energy of the particles ie. E = mgh
 
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
Back
Top