Rise Definition and 269 Threads

The FAQ by @bcrowell cites an explanation by physics netizen John Baez as to how entropy rises when a star loses heat and contracts. However, the linked explanation falls short of describing the key role that gravity must be playing. The FAQ by @bcrowell discusses why a low-entropy state of...

The only way I get this is to make a the vertical acceleration at the bottom corner and g the horizontal acceleration there. This is from Halliday & Resnick's Physics. I've been unable to find anything there or in REA's Physics Problem Solver. Thanks for any hints submitted.

Hello. I am creating a boost circuit and there is a lot of problems while testing. Before creating circuit i have simulated circuit in modelsim. Problems. 1. Sudden voltage rise from 40% to 50 % dury cycle. ( i am checking each duty cycle ) 2. When applying a gate voltage to mosfet the the...

My answer given below seems incomplete. Since warm air causes the air to expand in volume, so its density becomes less as compared to the colder air at the top of the room. After this, I generally find all books saying the less dense air rises and more dense air from top comes down and...

https://www.caryinstitute.org/news-insights/media-coverage/lethal-tick-borne-disease-spreading-us-driven-climate-change Certainly ticks have been a major problem in the NE US with respect to Lyme disease, Ehrlichiosis, and Babesiosis, and now we have Powassan virus to add to the list of...

How did you find PF?: Google l was asked how hot would our IT space get if we lost all air conditioning. The space is 20' x 15' x 10', We keep set point at 70 F and have 80 kW of load. Assuming this exists in a well insulate container with 20 racks of equipment. Doesn't have to be perfect but...

If I look at the specific heat equation mentioned, then I would be inclined to think that without heat energy being added to the gaseous mass its temperature cannot rise. But, if some form of energy like chemical energy in gaseous mass could be directly converted to internal energy of the same...

The text gives the answer as 92ºC. The answer is arrived at by doing ##Q=Mgh=mc\Delta T##. But it is unclear to me if they are the same. I checked the coefficient of friction and it definitely seems to be considerable. Is the entire PE lost by the truck going to result in increasing the...

Summary:: Given a known closed space/apparatus ( e.g. constant volume, pressure, density, current, temperature, voltage, spark gap distance - let me know if I missed something) how would I compute the change in gas temperature. Hello, Given a known closed space/apparatus ( e.g. constant...

Summary:: How to calculate the rate of heat transfer between hot external water and cold internal water in a pipe. The image attached is my attempt at the question however, I find myself stuck trying to work out internal and external heat transfer coefficient.

I have been wondering about submarines for a while, and especially their ability to sink and rise on command. I understand that they do this through ballast tanks and replacing water with compressed air, which increases the buoyancy force and helps them rise. (I understand that my knowledge is...

If we consider that the heating of the products created in the combustion of paper to be an almost adiabatic process (as it's extremely fast), then $$T^{1.4} P^{-0.4} = const. $$ If we double the temperature, we multiply the pressure by 11.3 The density of an ideal gas is $$ \rho=PM/RT$$ If we...

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(The picture below is my drawing. I followed the instructions of the problems and drew for reasons of clarity.) Let me start by writing down the given details : Volume of drum ##V_D = 0.05 m^3##, mass of drum ##m_D = 5 kg##, height of water column (initially) ##h_W = 1 m##, base area of water...

So, I was studying about general properties of matter and topics like surface tension. I came across the phenomenon of water rising along a glass plate like in the picture. I looked for some mathematical interpretation of this on the internet and in some books. [![enter image description...

When designing a panel, it is imperative that you keep the components inside at a temperature which they can operate optimally at; allowing the air temperature to go above this limit can cause component failure and fire. To assist with calculating the air flow required to keep the components...

WARNING! This thread contains spoilers for Star Wars: The Rise of Skywalker. If you have not yet seen the movie, we strongly encourage you to turn around and return once you have. Please use this thread for discussions about The Last Jedi, including spoilers. :smile:

According to this definition I am unable to understand why does surface tension acts tangentially to surface of contact of liquid and capillary tube. And is the force of surface tension balancing the adhesive forces which lead to capillary rise OR it is the reason behind the capillary rise?

Good Morning, I am not coming up with an answer in my search, could anyone confirm or deny whether a circuit conductor would experience more temperature rise with three-phase current than if the same R.M.S. current was single-phase. Alternating Current, 60 Hertz. If you want to know why I want...

I have a friend and he complained that at school they are teaching that warm air rises. He said it's wrong. He said instead the cold air sinks. Is this true?

ESL: Since valuable discussions are being made and then threads closed, here is an input: Melting ice to liquid water, will gather around equator because of gravity @lomidrevo

I'm pretty sure that everyone knows that if you put an ice cube in a cup of water, and leave it for some time for the ice to melt, the level of water in the glass will not rise. (you could use that principle where that guy was in the tub and said "Eureka!" and then ran around naked). Now, my...

Here is the BBC article, I've read today. Conclusion from the original study: This sounds really alarming to me.

Ok, we've got the first trailer/teaser from the next Star Wars Movie, which is named "The Rise of Skywalker": (it looks promising to me, and I hope it will be better than "The Last Jedi" which was a bit disappointing to me) Star Wars: Episode IX – Teaser

I know that the height in general is goven by 2σcos(θ)/(ρgr). So the maximum height can be 2σ/(ρgr) with cos(θ)=1. But the answer given is c.

Homework Statement [/B] Oceans cover 2/3 of the earth’s surface, with an average depth of 3.7 km. The average surface temperture is 17◦ C. Taking this temperature as representative of the entire ocean, and knowing that the coefficient of volume expansion for water at this temperature is β = 1.7...

Hey i have these ideas in which i use helium baloons. I wonder how high does it go and what is the gravity force and pressure at this point?

In the follicular phase, once the estradiol level reaches a certain threshold, it causes a switch from negative feedback to positive feedback on LH & FSH. That is why we have a surge near the end of the follicular phase. My question is, what makes estradiol rise and reach that threshold to...

Hi there! I'm teaching about rain shadows to 6th graders, and I've reached a barrier in my content knowledge. For the water cycle to work, warm, wet air near Earth's surface has to rise. In general, warm air is less dense than cold. However, due to air pressure, air near Earth's surface is...

I'm looking for a little help here. I'm just a relatively regular Joe here though, so any complicated formulas are likely to go right over my head. What I'm trying to do is use the Ruby programming language to convert rise and run (slope) to degrees. See the attached screenshot... Assume x...

Homework Statement A solid ball with radius of 9.7 cm is released from the height of hs=88.1 cm on a non-slip surface. After reaching its lowest point the ball begins to rise again, on a frictionless surface. How high does the ball rise on that side? Express your answer in cm. Homework...

Hi Everyone! There is a type of CO2 laser cutter power meter on the market (Product link removed) The meter uses a block of black anodized aluminum bonded to the end of basically a mechanical meat thermometer, and has a zero adjustment on the back of the face to set the base temperature to...

The recent rise of incentivized competitions for humanity has prompted me to create this thread, to tell PFers what's out there and to share my meager experience in "almost" entering one. The largest and arguably most influential one has been the XPRIZE organization which finds sponsors and...

I am looking for an explicit equation that shows that a sample with lesser volume will reach higher temperatures when irradiated than a sample with a larger volume. The samples in my project are biological tissues which are being irradiated by a laser. In my experiment, using a thermal camera I...

I was surprised to see this in a 'pop science' article a few years ago ("Ask Marilyn"), but quickly found the source, which appeared reputable (to me). But I have not seen any follow up. I finally got back to it. https://www.nature.com/articles/ngeo1476 To stay within forum guidelines, please...

Here's an interesting article by the AMS about mathematics in Sub-Saharan Africa. Also note the quotation on top: Mathematics knows no races or geographic boundaries; for mathematics, the cultural world is one country. (David Hilbert) http://www.ams.org/journals/notices/201807/rnoti-p798.pdf...

Homework Statement A 80.4 kg hiker uses 212 kcal hr-1 (3 s.f.) of energy whilst hiking. Assuming that 20% of this energy goes into useful work and the other 80% is converted to heat within the body, calculate the temperature change, in units of Kelvin (K), of the hiker's body during a 1.6 hour...

It seems that a partial solar eclipse is one in which the eclipse circle never completely rises, and it essentially is only a sunrise or sunset eclipse, with the point at which it goes from sunrise to sunset being that location in the polar region where the eclipse is at "high noon" but which it...

There are 2 types of temp rise measurement for electrical devices, 1)resistance type 2) thermocouple type (direct measurement) My query is 1) which method is superior and please explain me the reason. 2) Which gives higher value of measurement? Thanks in advance.

I know there are many factors that affect this question, such as altitude etc, but in its simplest form... - How fast does a parcel of air rise if, say, the parcel of air is at 5 degrees centigrade in a room filled with air at 0 degrees C. (Maybe I should be using Kelvin?). Just need to get an...

This may sounds like a stupid question but... If you were to use a subsea lifting bag filled with O2 it would rise to the surface. Would the same happen with CO2? I assume the density of CO2 is different so the amount required would be more or less than O2, but it is still less dense than...

Homework Statement Why there's no pore pressure due to capillary rise at point A and point D ? There's only pore pressure due to capillary rise at B .. Homework EquationsThe Attempt at a Solution i think the author is wrong . There's should be also ore pressure due to capillary rise at A and D...

When a magnetic field is applied across the left part of the tube , it's level rises as shown . I would be grateful if someone could help me understand why this happens . Thanks .

Homework Statement : See below paragraphs[/B] Homework Equations : I'm not sure on which equations I need.[/B] The Attempt at a Solution : I'm so sorry, this really isn't my strong point. Using the figures below, the tank surface is 113.184 sq in. The side pipe has a cross section area of 3.14...

Hi! According to the book "Renewable Energy on Power Systems" by Freris & Infield, the voltage rise due to injection of power in pcc can be estimated from the Thevenin equivalent representing the network "upstream" pcc (Figure 1). The Thevenin voltage can be taken as the nominal voltage in the...

Better stock up now as graphing calculators are becoming antiques just as slide rules did in the late 1970's. https://qz.com/977987/thanks-to-the-startup-desmos-the-reign-of-the-texas-instruments-100-graphing-calculator-in-schools-is-finally-ending/

Homework Statement A.[/B] Someone is walking outside when the temperature of the air is -10°C. The metabolic rate of walking is 140 Cal/m2hr, and the usual muscle efficiency (20%) applies. They are completely covered by clothing with a coefficient of thermal conductivity of 0.36 Cal-cm/m2hr...

Let's say you have a circuit connected to a 15 volt battery. If current travels from the negative terminal of a 15 volt battery to the positive terminal, the voltage is said to rise 15 volts. I believe this is right, but correct me if I'm wrong. Assuming that is right, then does that mean that...