Hot Definition and 572 Threads

Homework Statement (c11p34) You pour 160.0 g of hot coffee at 75.0 oC into a 230.0- g glass cup at 24.0 oC. If they come to thermal equilibrium quickly, what is the final temperature (in oC, enter deg in asnwer box)? Assume no heat is lost to the surroundings. Homework Equations (I don't even...

Homework Statement A hot-air balloon has a volume of 2000 m^3 and generates a lift of 2720 N (assume the outside temperature is 20◦C with an air density of 1.2 kg/m^3). A)What is the density of the air inside the balloon? B)How many moles of air are inside of the balloon (the molecular mass of...

Homework Statement [/B] In hot pursuit, Agent Logan of the FBI must get directly across a 1200-m-wide river in minimum time. The river's current is 0.80 m/s, he can row a boat at 1.60 m/s, and he can run 3.00 m/s. Describe the path he should take(rowing plus running along the shore) for the...

Homework Statement You would like to put a solar hot water system on your roof but your not sure if it's feasible. A reference book on solar energy shows that the ground level solar intensity in your city is 800W/m^2 for at least five hours a day throughout most of the year. Assuming that the...

Homework Statement A copper vessel of 100 gr contains water, 150 gr, and 8 gr of ice. a 100 gr piece of lead at 2000C is thrown in. what's the final temp' Homework Equations Specific heat copper: 0.093 Specific heat lead: 0.031 Melting heat water: 79.7[cal/gr] The Attempt at a Solution On the...

I wondering what actually happens when you brew coffee (or tea) with hot water. Every source I can find simply talks about how long you need to brew it to "draw out" the flavor or "release" the caffeine. I'm interested in what's actually physically happening to the coffee grounds that makes it...

Homework Statement Assuming normal pressure and temperature outside, and normal pressure inside, what should be the inside temperature (in Celsius) if the hot air balloon has diameter 17 meters and carries 446.3 kg load? (Except the mass of air inside, everything else is included in the...

During summer my swimming pool is 23° C and my loft air is 53° C. (73° F / 127° F) The sun shines on the metal roof with 1x10^5 to 1x10^6 W and I hope to move 10.000 - 20.000 W to the pool. To move the heat down by an external water circuit to the water/water heat exchanger by the pool...

Dark matter can't radiate heat (i.e. no electromagnetic energy). 1. Might it retain the original temperature at the moment of its creation? 2. If temperature is directly related to pressure and both are inversely related to volume, then would cosmic expansion mean that dark matter is as...

Working on a project where we have been asked to utilize waste heat from a combustion process in order to increase the temperature of oil in a separate process. The hot air from combustion is at 340C and the oil is at 22C with a target temperature of 65C I have not seen any hot air heat...

Hi, so I have this interesting theoretical question. Consider scenario: A hot sauna. The heat source is a number of stones which take heat from a chimney which takes heat from a burning wood. Periodically you pour some water on the stones to create some steam. This, of course, cools down...

According to Einstein (e.g. in his book The Meaning of Relativity), a clock rotating about a central clock will be judged by the central clock to run slower than the central clock. This means that a signal sent by the central clock will be perceived by the rotating clock as being of a higher...

This question has puzzled me for a long time and there have been many kinds of answer for it. The most sensible explanation I have heard is this one. http://physics.stackexchange.com/a/33026/40382 But then I found another explanation at...

If heat flow is the momentum change from a faster moving atom or molecule to a slower moving one, and momentum is mass x velocity is it possible - for a very limited amount - for heat to flow from a slower (colder) heavy atom to a faster moving (hotter) atom ?

Heat flows from higher temperature to lower temperature. The body temperature is 37 celcius, but still if that's the surrounding's temp., it is very hot. Why so? Shouldn't 37 celcius be the perfect temp?

In an AC circuit, we know that the polarity inverses, and what i know is that the flow of current also will therefore inverse.. which means that the live will become negative and the neutral will become positive.. What i can't understand is how the polarity inverses but the live is still the hot...

Hi everyone, I'm working on a project at my university and I'm having trouble figuring out how much heat escapes a hot tub when it's at 42°C and outside temperature is at around 7°C (I live in Iceland). I'm considering the hot tub closed with a styrofoam cover about 10cm thick and walls of the...

Light bending in the "hot plate" model of curvature In the Feynman lectures, feynman describes the hot plate model of space curvature and shows that light is bent around the center of the plate, see Fig. 42-6 http://www.feynmanlectures.caltech.edu/II_42.html#Ch42-S1 However, the hot plate...

Homework Statement A hot air balloon with a total mass of 7000 kg carries a gondola (or basket) which includes 1000 kg of sand bags fixed to the outside. While hovering at a fixed altitude, sand starts leaking out of thebags at a rate of 50 kgs-1. Determine the velocity of the balloon at the...

Generally for bathing purpose, we heat water to higher temperature say T1 than the temperature at which body is comfortable say T0 (is T0 = 70 degree Celsius?) & add some quantity of cold water to it to have the temperature of water = T0. Is the process energy efficient? What is the best...

Homework Statement I'm having a slightly hard time with a topic we are studying at school 'the evolution of the universe'. My first question relates to the Big Bang Model itself; does the Big Bang Model itself describe the evolution of the universe after the Planck time up to this point...

I have tools that are made of metal and very reflective and shiny. If shiny objects reflect light waves, how is it that my tools get too hot to touch if I leave them in the sun (in the summer months)? Are the tools absorbing other forms of EM radiation?

What temperature would the human body need to be in order to sustain all necessary metabolism reactions in the absence of a catalyst? I know this is unreal, I am just curious of an order of magnitude estimate.

Took apart a hot plate, nichrome is touching directly to the iron?? How is it not shorting out?

If I was going to build a fusion device for energy production I would build a cylinder filled with fusion fuel and the fusion would happened in the center. First it would be hard to start the fusion with relatively cold fuel. After a while of heating, the surrounding fuel would be hotter even if...

Closed, collapsing universe+only photons at first --> matter when hot? Suppose we had closed, collapsing universe with a uniform thermal distribution of low energy photons like that of the CMB and no other matter (I suppose we must pick the initial conditions right for collapse to occur) . As...

Homework Statement A hot air balloon with V = 500 m^3 is floating in the air without moving. The air outside the balloon has a density of 1,20 kg/m^3, and the hot air inside the balloon has a density of 0,75 kg/m^3. Calculate the total mass of the hot air balloon. Homework Equations...

Consider any of the latest maps of the temperature fluctuations of the CMB. Such a map can be considered a 2 dimensional topographical map of the surface of a sphere, high points hotter, low points cooler. Consider the contours that divide such a map into the two regions, fluctuations hotter...

Homework Statement I just completed a lab in class where we heated a copper pipe and measured the temperatures at 25 different locations. Each of these locations is called a node. The goal is to find the convection losses by using the First Law (qc1 + qc2 + qc3 + qc4 + qrad + qconv = dECV/dt)...

Let me give you a glimpse at my research. I uploaded a video of my latest simulation on youtube, . You can see the formation and evolution of vortices in hot plasma such as fusion plasma. The subtlety is that these vortices do not live in the real, everyday-life 3D space, but in an...

A couple questions about a "hot room" concept. I had an idea that I may try to implement should I ever get around to building my dream house. I think of it as a "hot room". The idea is that there is a utility room which is positioned to receive most of the wast heat generated by household...

Homework Statement A hot air balloon of mass 425 kg ascends from the ground level and accelerates at a rate of 1.25 m/s/s for 25 seconds. How much work is done by the upward buoyant force on the balloon? (conceptual) A certain amount of work W is required to accelerate a car from rest to a...

I was driving home today in my car, which had been parked in an exposed spot with a cold wind on it. It was very cold when I got in. I turned the heater (water valve control) on full but only had the fan on '1'. After a couple of miles, the engine thermostat cut in and the water temperature...

Homework Statement A solar hot water system is designed to supply 100% of the hot water demand of 0.6 m3/day when the isolation on the tilted collector is 22,000 kJ/m2 with a collector efficiency of 50%. The tap water temperature is 8ºC and the desired hot water temperature is 58ºC...

Hello,Im reading a article about water spliting device in which all necessary charge carriers for water spliting arise from surface plasmons. This is the article: http://www.nature.com/nnano/journal/v8/n4/full/nnano.2013.18.html#f1 So i do not understand how charge carriers arise form...

I need to model the buoyancy of a hot air balloon in Simulink and VRML. I want to the system to be the balloon (simplified to a sphere) with a constant temperature heat source in the center with convection cooling the balloon. The heat source will turn on an off. I need to get the average...

Homework Statement A 85 gram piece of metal is heated to 98°C and placed into 200mL of water insulated at 20°C. If the equilibrium temperature is 26.50, find the heat gained by the water. Homework Equations 200 mL = 200 g. 85 g x 98 degrees celsius x specific heat of metal = 200 g x...

Say you're in a place either 15 degrees north or south of the equator where average temperatures are over 25C (77F), a large majority of days are either cloudy or rainy and there isn't any wind. You need 50Wh a day for your needs and the battery you have happens to have a capacity of 50Wh as...

http://www.iflscience.com/chemistry/hot-water-freezes-faster-cold-and-now-we-know-why I thought that this had never been shown to happen with closed containers. I always thought that this was an issue of open containers allowing for evaporation and hence a smaller amount of frozen water, and...

This question is really starting to bug me!:bugeye: Consider for example Io is orbiting Jupiter and the force of the gravity pulling the moon towards the planet vs the momentum pulling in the other direction creates friction in the moon's core. First of all, this should heat up the moon. But...

When tiny droplets of hot water touch your hand you don't feel much pain but when large amount of hot water spills on your hand it will cause serious injuries. Why? - is this due to the heat energy in the tiny droplets of water is lesser so the energy transferred to the hand is lesser...

Homework Statement Consider two systems which together comprise an isolated system, but are initially not in equilibrium with each other. The temperatures of the two systems are T_1 and T_2 and the internal energies are E_1 and E_2. The systems are separated by a diathermal wall and only...

Say I have a volume of hydrogen gas that is raised to a temperature T so that 99.9 percent of the gas is ionized. If now, with the plasma at some pressure P, the volume is compressed a small volume dV such that no energy leaves the volume I'm curious of a total accounting of where the energy PdV...

I have a portable compressed air cylinder - pressure 10 kg/cm2 - powering a small reciprocating pneumatic piston/cylinder assembly.To increase the usage time of the system,I want to fit electric air heaters in the cylinder on both sides of the piston as well as in the compressed air...

What's the difference between cold moving air and hot moving air? For instance, suppose you put two fans, of the same type, each in one room. One room is cold because the walls are covered in ice and one room is hot because due to the effect of heaters. Turn both fans on and the air flow, the...

I am interested in the math involved to calculate the ideal natural teardrop shape for a hot air balloon. I want to learn the details of what is involved to calculate this accurately. I read this https://www.physicsforums.com/showthread.php?t=658802 which was a really nice start, but it...

Homework Statement 2)A certain heat source (a heat reservoir or thermal reservoir), is always at temperature ##T_0##. Heat is transferred from it through a slab of thickness ##L## to an object which is initially at a temperature ##T_1 < T_0##. The object, which is otherwise thermally insulated...

Hi; I want to select a battery 12V-70AH for a UPS (Un-interruptible Power Supply) but problem is “temperature”. The environment temperature where UPS would be installed can be raised up to 42C. So the flooded lead acid batteries can not work there as each 8C of temperature rise decreases the...

Hello everybody. I am just a man who interest in physics. And with the question I concern above is the reason I join this forum. Nice to meet you all To the main point I want to know exactly that, Is energy of one person enough to generate hot air for lift balloon system and himself? By any...

Damn, I'm burnin' up here. Aren't you dyin' down there in Olympia Lisab?