studiot

Just to make emphasize what swansont was saying. A Helmholtz resonator works quite differently from a tuned pipe. Essentially it works by bouncing (vibrating) the plug of air in the neck of the bottle up and down against the springiness of the air in the body of the bottle. This is achieved by raising or lowering the pressure just outside the mouth of the bottle. This causes the air in the neck to move in or out, pressurising or depressurising the air in the body of the bottle The volume of air in the bottle opposes this and the resonance depends upon the volume of the bottle. Note that it is not necessary for the bottle to be sealed or enclosed. This is how a vehicle exhaust silencer works, by having changes in pipe size causing this effect on the exhaust airflow.

Or perhaps a Heating Engineer. Look up 'Heat Pumps' Is this what you are interested in?

This is a duplicate of your earlier thread. http://www.scienceforums.net/topic/103650-which-science-profession-i-need/ You have not supplied sufficient information to consider the problem. Both the airflow details and temperature are required. Also are you aware there are two definitions of humidity? Absolute humidity and relative humidity? https://www.google.co.uk/?gws_rd=ssl#q=absolute+humidity&*

I couldn't agree more that this is a brilliant video, Delta1212. +1 In particular, wallflash, you should study it more carefully. The presenting Professor of Physics, who also deserves full credit, actually describes why your post#5 is wrong between 2:40 and 2:57 on the video.

Rather than concentrating your fire power on one small and relatively insignificant part of the design, you should consider all aspects of it. The major influences on system performance come from elsewhere. For instance, do you not wash more in the summer? The industry reports that there has been a shift from the major energy user being home heating/cooling towards water heating in recent years due to greatly improved building insulation. There are many other aspects of the installation to consider, before compressor siting. We have two heat pumps in the family. Both are air to water. One is completely outside and only heated/spent water is transferred between the unit and the outside engine. The other is completely inside and only natural air is transferred, via a duct. This is because it is in a third floor London apartment and local planning regulations require it this way. Both also utilise a part of the system you haven't mentioned; a heat store. This type of system is gaining popularity.

There was a thread about heat pumps a while back that had some useful information. http://www.scienceforums.net/topic/84339-heat-pump-applications/?hl=%2Bheat+%2Bpump I have since installed a residential heat pump and thought I had recently started a thread to record experience and for folks to discuss it, but I can't find it at the moment. So here is a link to a really good book about them with lots of information tables and photos of real installations. http://www.crowood.com/details.asp?isbn=9781847972927&t=Heat-Pumps-for-the-Home You should be aware that residential heatpumps come in different types, depending upon their source of heat energy, which can be the ground, water (eg a stream) or the air. Further the way the heat is supplied also comes in different forms. So you can use the heat to heat water or air or even building fabric. The link you reference is known as air to air since heat is taken from the outside air and added to the inside air. Doing this costs less energy than using electric or gas (or other fuel) energy to heat the air directly. This is because you are inputting work to drive a machine that achieves this. Air to air types would be suitable for your area because you can reverse these to provide cooling in summer.

There is often a temperature difference between the mean fluid temperature and the temperature of obstacles. So for example you would be extremely uncomfortable if your jetliner was at mean atmospheric temperature at altitude. In such a case you would use the viscosity at the mean fluid temperature. If however your fluid was air being drawn through the fins of a heat pump exchanger, mean or average viscosity only has meaning when the air is well clear of dew or ice points. Each situation must be considered on its merits.

This recent thread in homework shows an interesting use of arclength. http://www.scienceforums.net/topic/103512-force-and-laws-of-motion/ Please also note that just because the plot region extends to infinity, it does not mean that the arc length of the plotted curve is infinite. For example the plotted arclength of x2 + y2 = 1 is finite whatever the size of the plot area.

Bringing metal into contact with anything can be tricky. Apologies for important missed word, EDIT Bringing charged metal into contact with anything can be tricky. Why not connect a non charged metal object and then charge it? This is how a point contact transistor was made. https://en.wikipedia.org/wiki/Point-contact_transistor

But it doesn't so why waste effort speculating? To answer your more reasonable second question, Gravity, electricity and magnetism have some similarities and some differences. This has long been known. Almost all of that time attempts have been made for a common framework, with varying amounts of success, but none have succeeded completely. More recently we have added two more forces to the list; these operate at sub atomic level and are called the strong nuclear force and the weak nuclear force. At this (sub atomic) level we can show magnetism and electricity are aspects of the same thing so we think of four fundamental forces of Nature. https://www.google.co.uk/webhp?sourceid=chrome-instant&rlz=1C1BLWB_enGB520&ion=1&espv=2&ie=UTF-8#q=four+fundamental+forces&* However at beginning level and for practical purposes it is best to think of 5 forces and use well established models.

I'm stuck out in the north of Scotland right now, so resources are limited but look here. https://www.google.co.uk/#q=sienceforums.net+momentum+bullet+and+block&* https://www.google.co.uk/#q=youtube+momentum+bullet+and+block&*

Since Nick has (against the rules) completed your homework for you, try o learn something from this. Nick has made an unstated assumption in his solution to the second part: Can you say what this is and why it is important?

This is a really good way to go about discussing a subject. +1 You have presented some basic observations, are they complete? That is Have you considered both plastic and glass lenses? Which side of the lens fogs up, or is it both? This is an important question that provides a clue to the answer. Have you looked at other glass/plastic objects, for instance window panes? Which side of a window pane fogs up?

Yes momentum balance is the key to this one, we had a long discussion a while back about bullets and blocks, where I posted links to a good Ytube video on the subject. Perhaps someone can find it, the search function is poor here.

It is a good idea to state the reason for each line in your working so that both the reason and the working can be checked on review. You have assumed constant acceleration along the 12m trajectory. Do you think this is correct? What are the vectors? Have you thought about resolving them vertically and horizontally? Is the acceleration constant vertically and horizontally or should they be treated separately? Have you thought about the work-energy theorem and equating PE, KE and work?

Looks like a jacobian matrix to me. Look here, particularly the examples. https://en.wikipedia.org/wiki/Jacobian_matrix_and_determinant

Returning to the OP topic; Here is a good presentation of he calculation of area of revolution, incorporatingand extending the idea of arc length. you can tab back to their presentation of arc length http://tutorial.math.lamar.edu/Classes/CalcII/SurfaceArea.aspx

Agreed but I don't see the relevance of why it should be expected to any more than just the arc length will distinguish between a parabola and another curve which just happens to have the same length.

Yes that was an extremely bad example to offer please delete it or add a note to that effect. The rest of my examples are good however. I did however take the OP to be a general question about arc length, and the reference to parabolas, movement or plots just an example.

To answer the original question, if the OP is still interested; Lines can exist in two or three dimensions so To find real world examples of use of the length of arc look for things that are linelike. In 2D say you are constructing a suspension bridge or a posttensioned bridge. Bridge cables are expensive, per metre, so the bridge owner only wants to pay for the cable actually used. The bridge builder on the other hand need to know exactly how much cable to order, so that he can do the work. So both have a strong interest in the exact length of cable. In 3D the manufacturer of electric windings needs to know the length of wire to complete the number of turns on a bobbin. As does a coil spring manufacturer need the exact length of spring wire for his coils. Those were all physical examples. Navigators and surveyors need to know the arc length on the curved surface of the Earth, a theoretical, but nevertheless important value. For a financial example related to plots, say you were saving money, at regular intervals. A the length of a plot of money v time would tell you how much you had at any given time.

Geordief you may remember an old saw about two short planks (not referring to you of course) Anyway you might like to consider / be intrigued by this article on the subject of Maxwell's equations, the invariance of c and two short planks.

Do the lifeforms have to be living? There's over 3 billion years of lifeforms available to study in the earth sciences (eg paleototany, paleonology etc) as well as a good dollop of physics in geophysics.

Or electro-osmotic or some other electrochemical process?

+1 for pointing this out. You may need a dynamometer one day but I would have thought a simple homebru friction brake and sensitive spring balance would suffice until then. Alternatively you could go back to Joule and drive some paddles in a viscous liquid and measure the temperature rise.

I am expecting a long telephone conversation with someone in Germany in a couple of minutes but I will expand on the headings I have introduced and explain what I mean later.