Recent content by arashmh

We know that when sound travels through solids like a wall, the air molecules interact with solid molecules in porous medium to transmit the information hidden in sound wave.The question is that why no noise is added to someone's voice when we hear it from other side of a concrete wall ?

You are very detailed in your explanation. I appreciate it. Ok, we know that if the stream of water has enough path to fall freely , after some time , it will break down to some branches and finally into a spray. how this ball-spring model explains this in molecular level . by the way, feel free...

I can't agree more Klimatos. What i want to know is a description of what happens at the molecular level. These different explanations ( Bernoulli and molecular attraction) shows that we do not look for the origin of the forces. We know that each known force is exerted from something ON...

Dear Cjl, i am a phd student of chemical engineering and i know every single detail about conservation of mass and I'm sure u know it too and in detail . but my point is that , the molecules do not know any thing about conservation of mass as we do :) the thing that makes me confused is that...

ok, and what would have been violated if the stream didn't make a conic form with the presence of tension ?

Chris , that was awsome! now can u explain what forces the molecules to form a conic shape ?

OK, bernoulli works always . but we have to keep in mind that this experiment with paper leads to the same result even if there is no curve in water stream , i.e when the flow rate of water is so tremendous! So i c that this bernoulli effect , affects the water stream , but it;s just one of...

Thats a clever point u pulled in :) but i feel it has to do something with molecules of water , not the air surrounding it.

so , up to now, the summary is this : the conic form of the water stream has nothing to do with the air surrounding it , so bernulli goes out of the consideration. we know that a force pulls the molecules toward the center . if it's not the pressure of air surrounding it , the only remaining...

Exactly. And that force is the pressure differential brought about by the water moving with respect to the surrounding air. This Bernoulli Effect is often ignored or overlooked. A force that can pluck a forty-pound sheet of plywood out of the bed of a pickup truck, can lift a fully-loaded...

uhu, can we formulate the problem to c when the stream finally divides into multiple streams and sprays?

I c , by the rope i meant the pulling of the rope. now , in your analogy we pull the central rope only or all ropes ?

Thats a good point, can u explain how preventing from being a spray bring the energy to its minimal level ?

Dear Drakkith Thanks for your interesting example. I assume that in this analogy, the rope plays the role of gravity force , right ? why should we just pull the middle rope while gravity acts on all molecules? If we pull every rope upward , all balls will displace horizontally for a little and...

Instead, the reason is simple continuity. The mass (and volumetric) flow rate of the water must be the same near the bottom of the column of water as it is near the top, since clearly water isn't being generated out of thin air in the middle of the column. Since the water is speeding up due to...