Recent content by ShizukaSm

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    Trial-and-Error with thermodynamics tables

    I know there`s a method in thermodynamics when you need two variables, have one state equation and know one information of the final state, where you can progressively approximate and discover the two wanted variables. I know about that because my professor did it in class, and while I also...
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    Water in a piston-cylinder device losing heat

    I think the problem wasn't very well written. In state 2 all water is already condensed (that's what I thought initially, though your theory was also plausible in my mind, and later I confirmed that in the solution manual). I suppose the only way to figure out that the third state was saturated...
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    Water in a piston-cylinder device losing heat

    Homework Statement The Attempt at a Solution Let's divide it in three states. E_1(\text{Initial state}) \\P = 3.5 \text{MPa} \\T = T_\text{sat@P} + 5 = 242.56 + 5 = 247.56\text{ C} \\ h_v = \text{Known value (table)}\\ v_v = \text{Known value (table)} E_2(\text{When the piston hit the...
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    Pot cooking food and being cooled, how does the pressure change?

    Thanks, that's a clever way of doing it. Hmm, that's exactly what I need, but I am highly confused, I don't understand why the pressure drops to 2.34 kPa if it also condenses and I don't think I understand equillibrium vapor pressure very well. 1) Let's say the water went to 95C...
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    Pot cooking food and being cooled, how does the pressure change?

    Right. Thanks, but I understand it up to this point, a vacuum will be created (since it`s not a pressure cooker and doesn`t have a pressure vent), I just don't understand how to quantify this vacuum created.
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    Pot cooking food and being cooled, how does the pressure change?

    Homework Statement A person cooks a meal in a 30-cm-diameter pot that is covered with a well-fitting lid and let's the food cool to the room temperature of 20°C. The total mass of the food and the pot is 8 kg. Now the person tries to open the pan by lifting the lid up. Assuming no air has...
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    Opening the refrigerator door to cool a room.

    Right, indeed. I was also wrong about how a refrigerator works. It seems that the compressor regulates itself differently depending on the temperature, adjusting its work. That makes much more sense. Thanks.ks
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    Opening the refrigerator door to cool a room.

    I'm well aware that the default answer to this textbook default question is "it doesn't work", but still, I believe it does. To cool the insides of the refrigerator, the compressor must do work, and since the efficiency isn't 100% you are constantly warming the whole room to cool it's...
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    How many times must an 80 kg weight be lifted to burn off .5 kg of fat?

    Right. I agree and understood. But considering a real-life situation, would it be plausible? Or is the fact that it's a constant deceleration (decelerating the iron until initial point, I mean) somehow resultant in smaller work done?
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    How many times must an 80 kg weight be lifted to burn off .5 kg of fat?

    An athlete needs to lose weight and decides to do it by "pumping iron". How many times must an 80 kg weight be lifted a distance of 1 m in order to burn off .5 kg of fat, assuming that that much fat is equivalent to 3500 Cal? Q = n\left(m\cdot g \cdot h\right)...
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    How is the slope of the temperature graph determined?

    Oh, yes it does! Thanks a lot:smile:
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    How is the slope of the temperature graph determined?

    In a series of experiments, block B is to be placed in a thermally insulated container with block A, which has the same mass as blockB. In each experiment, block B is initially at a certain temperature TB, but temperature TA of block A is changed from experiment to experiment. Let Tf represent...
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    Frequent assumption made (z R)

    Frequently, when a length is bigger than another (say, an axial distance is bigger than the radius of something related) a certain assumption is made and the smaller length is "removed" from a formula. It's hard to describe, so let me show an example: The magnetic field from a bobbin at an...
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    Finding friction on a onedimensional tube

    Find the friction coefficient between the bar and the surfaces. Both surfaces are equal (and thus have equal coefficients). Ok so, my problem is that, generally in physics when I assume an wrong direction for a vector, I will be able to discover that in my answer (generally speaking the...
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    Calculate the electric potential of a charged bar

    Thanks ! I actually think I got it now, I tried changing the origin (placing the bar in the negative sign, for instance, to change my perspective) and finally grasped this concept. I still don't understand very well why I can't have ##V_a## without the information that ##V_\infty = 0##, can't...
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