decrease Definition and 231 Threads

Homework Statement A student performed the reaction in this experiment using a water bath of 90 degrees C instead of 50 degrees C. The final product was tested for the presence of phenols with ferric chloride. This test was negative (no color observed); however, the melting point of the dry...

Ive read on loads on places that tell me this but don't explain why. They explain the closed loop gain drops off because the open loop gain in their 'real' equations is no longer infinite/very high so the assumpstions that lead to ideal equations fail. but nowhere can I find an explanation...

Before a few days ago I always thought that when transformers decrease the voltage, the transformers increase the current. Then on another thread at Physics Forums, people have told me that when transformers decrease voltage, they don't increase the current. The PFers told me that the...

I have read that most power lines on utility poles in residential neighborhoods carry about 4800 volts. My sources say that the transformers on utility poles decrease the voltage from 4800 volts to about 220 volts in most houses. Someone told me that the utility companies decrease the voltage...

Hello, For simplicity's sake, let's take a np junction. Say we connect the left side (n-pole) to a POSITIVE voltage; this is called a reverse bias, because it will result in a small current from n to p. In other words: electrons will travel from p to n across the junction (and holes will...

Homework Statement What is the approximate decrease in pressure in going 31 m above the surface of the lake? Air at 20 degrees C has density of 1.2 kg/mcubed. The pressure at the surface of the lake is 104 kPa Homework Equations Pressure = F/Area Force = density*area*height*g...

Homework Statement A gas is contained in a metallic cylinder fitted with a piston. The piston is suddenly moved into compress the gas and is maintained at this position. As the time passes the pressure of the gas in the cylinder- a)Increases b)Decreases c)remains constant d)increases...

Let V_B be the rate of decrease of the magnetic fields \frac{dB}{dt} For the 3rd path: \oint E\cdot ds = -\frac{d\phi _B}{dt} = -\frac{{d\phi _B}_1 + {d\phi _B}_2}{dt} \phi _B_{(t)} = A_{(t)}B_{(t)} The area is constant, it's only the magnetic field that's changing: \phi _B_{(t)} =...

General entrpy question from a book- (not a homework quesiton): When a room temp object is placed in a refrigerator, heat flows out of object and its entropy decreases. Indeed, the refrigerator may be said to be a device for sucking entopy out of warm objects. How can such a decrease in...

the function is: x/(x^2 - 9) i have found the horizontal asymptote(y=0) and vertical asymptote (x=3, x=-3) the first derivative is giving me problems =(

A golf ball without dimples experiences more drag because the deflection area of the airflow around the ball is larger which means that the pressure drop behind the golf ball is also higher. The increased drop in pressure creates a suction vacuum behind the golf ball which pulls it back and...

Homework Statement Radioactive iodine (131-I) has a half life of 8 days. How long does it take for iodine to be reduced by factor of 100? Homework Equations N(t)=N(o)e-kt k=ln100/t1/2 The Attempt at a Solution N(t)=N(o)e-kt N(t)/N(o)=e-ln(100/8)t Now I'm stuck. I would...

Homework Statement A simple pendulum consists of a small object of mass 2.4 kg hanging at the end of a 2.0 m long light string that is connected to a pivot point. (a) Calculate the magnitude of the torque (due to the force of gravity) about this pivot point when the string makes a 3.0° angle...

hey, I was reading Aircraft Design: A Conceptual Approach by Raymer and i came across the following line. ' The aerodynamic efficiency of an aircraft, expressed as the lift to drag ratio is greatly reduced during low level, high speed flight as well is its engine efficiency. ' Can someone...

hi We all know when velocity of fluid increases then cross section decreases for same mass flow rate and this can be well seen at water flowing from a height as in waterfalls. But why this doesn't happen when water flows down through a vertical held pipe of constant cross section. Well you may...

Hello everyone, I always though when reactants are heated up, there are more collisions and more like a reaction is to take place. However this is not the case for spontaneous reaction according to Gibbs equation. Why is that? Thanks :smile:

anyone tell me why melting points of any substance decrease when we add any other material

Homework Statement Does the current drawn by an electric motor increase or decrease as the motor starts from rest? Homework Equations The Attempt at a Solution I can't find an answer anywhere. I would think it would decrease because less power would be required to keep the motor...

y=-(x-3)^5(x+1)^4 For this function currently i have: degree: 9 sign: negative ? quadrants: I, II and 4 Roots: x=3 and -1 y-intercept= 243 domain: x belongs to E range: y belongs to E INTERVALS of INCREASE : ? INTERVALS of DECREASE : ? End Behaviors: As x approaches -infinity, y...

I am a trumpet player at a conservatory and I've been told for years that reducing the amount of air pressure through the trumpet will increase the volume of air that flows through the instrument. The people that have told me this always cite Boyle's law, but my understanding is that Boyle's...

Homework Statement Consider the behavior of the circuit, when various values increase or decrease. (Select I-increases, D-decreases, If the first is I and the rest D, enter IDDDDD). A) If R3 decreases, the current through R4 ___. B) If R3 decreases, the current from the battery ___. C)...

I know there is venous pooling due to gravity but how does this exactly affect pressure exerted on the walls of blood vessels. Does systolic or diastolic blood pressure decrease? Thanks!

Hi could someone please explain how this can be done please 1. The population P satisfies the differential equation dP dt = X(P) − Y(P) , where X(P) is the birth rate and Y(P) is the death rate. Find the general solution P(t) to this differential equation for the case that X(P) =...

Homework Statement A stone is thrown into a quiet pool of water. With no fluid friction, the amplitude of the waves falls off with distance r from the impact point as: A. 1/r3 B. 1/r C. 1/r1/2 D. 1/r3/2 E. 1/r2 Homework Equations I can't think of any wave function accounting for...

I gather the following: - A decrease in atmospheric pressure leads to a decrease in boiling point - Thermodynamics explains this using mathematics - A kinetic theory model can also be used to explain I need to know: - The science behind this occurring. Why does a lower atmospheric...

I considered entropy to never decrease in an isolated system, so I am a little confused when i read about how molecules 'self assemble' to lower interfacial energy which leads to an ordering of the system... Is this ordering not a decrease in entropy violating the law that it always...

Say in the far future when the universe achieves maximum entropy and all energy is rendered useless. Is it possible under ANY circumstances given all the time it needs to reverse entropy? I don't care about probability, does it break any laws in order of total reversibility of entropy turning...

Homework Statement A spotlight on the ground shines on a wall 12 m away. If a man 2m tall walks from the spotlight toward the building at a speed of 1.6m/s, how fast is the length of his shadow on the building decreasing when he is 4m from the building? Homework Equations x2 + y2 = z2 The...

This is not a homework question, but simply a custom problem from class. I've attempted to answer it but realized I was incorrect, and can't think of an alternative answer. Homework Statement A cart is sitting on a frictionless track. A string is attached to this cart, which runs over a...

This was a question on a homework assignment I had a few weeks ago: ""Intelligent Design" believers sometimes argue against evolution by saying that it is impossible for a system (i.e. a human being) to become so organized since everything tends towards maximum entropy. Do you agree with...

I did an experiment today, I put some magnesium in HCl solution (pH of around 1 or so) , but for some reason the pH decreased (turned more acidic), and my teacher said that's expected but didn't tell me why it happens. Enlighten me, please.

This was the problem before the one I am asking about (backstory maybe?) - Maybe relevant to my current problem \frac{dh}{dt}=-\frac{A_{h}}{A_{w}}\sqrt{2gh} Problem statement: It seems that, by placing marks on the tank corresponding to the water level at intervals of, say, one hour one...

Homework Statement "Water in a hydraulic press is subjected to a pressure of 4500 psia at 68 F. If the initial pressure is 15 psia, approximately what will be the percentage decrease in specific volume. Use Table 2.1 (below)." Homework Equations...

I was thinking about it, and the only thing I could come up with is that it reduces friction with the surface the object is sitting on and perhaps it distributes weight evenly?

Homework Statement A container of hot liquid is 180 degrees F. After 4 minutes, the liquid's temperature is 64 degrees F. How much longer will take its temperature to decrease to 32 degrees F? round to three decimal places Homework Equations The Attempt at a Solution I have no...

why? why not?

If you raise the voltage you must raise either the current or the resistance since V = IR. So how does a wire with higher voltage and lower current have less resistance? It should have more resistance to make up for the lower current.

N resistors (N>2) are connected in parallel with a battery of voltage V0. If one of the resistors is removed from the circuit, which of the following quanities will decrease? 1. the voltage across any of the remaining resistors, 2. the current output by the battery, 3. the total power...

Homework Statement WHICH OF THESE IS TRUE: The entropy of the universe can never decrease All heat engines operating between the same temperatures have the same efficiency Any process that includes adding heat to an ideal gas will increase the entropy of the gas All Carnot engines...

Okay, i am doing a lab involving crude acetaminophen and pure acetaminophen. The crude acetaminophen is supposed to have a lower melting point than the pure acetaminophen... how does that work and why? does it have to do with thermodynamics or what??

the decrease of the information v.s. chaos ?? One book about Chaos says that we can use the decrease of the information of the system to define whether the system is chaotic or not. I don't know why and how to do it? If you know about it, can you show it to me, or you can tell me the...

my aim is to lower the cut in speed of the horizontal turbines. I know wind speed has a brutal effect on turbine output, so I want to use horns to speed up air. I plan to put a horizontal axis turbine in the midle of the hexagon You see on the pic. Each side of the hexagon is like a...

Two loops have current flowing through them (see picture). The top loop lies directly above the bottom one. When the current in the bottom loop is increased, what happens to the top loop's current? Does it increase, decrease, go to zero, doesn't change or it depends on the relative values for...

Hi all. For a person trying to lose weight should they decrease their calorie intake or their fat intake or both. Sorry if its a stupid question, I know very little about this stuff. Thanks for any help.

Brain and skull Do you have a 50% chance of dying when your skull is opened for brain surgery due to intracranial pressure? How much can you decrease your odds of dying from that? And how much of the brain could be repaired from putting stem cells into the brain (the most possible during one...

Sorry but I suck at thermodynamics... Can entropy decrease LOCALLY, provided that the decrease is compensated by an increase in the rest of the universe (or whatever isolated system we are in), so that the total change of entropy is positive? Can you provide a sample phenomenon where this...

This question was in the exam I just sat, it was of a type I hadn't practiced, and I'd like someone to check my answer, as if it's wrong then I'm almost certain to have failed. At 7 a.m. I made a cup of tea; after adding some milk it is about 90 C. When I left at 7:30 a.m. the tea is still...

Hi, John Baez has written an interesting article on a subject I was looking for the answer to ( http://math.ucr.edu/home/baez/entropy.html ), but frustratingly he does not give the final answer! I have tried to figure it out and sadly failed. I even wrote to Baez but got no reply :frown...

Hi Guys, I am new to this forum and have a "quick" question. Say you had a laser pointer and you directed the laser through a glass block and then to a LDR why would the light intensity recorded be lower than without the glass block? What is happening to the light when it is in the glass...

One mole of certain gas is confined in a container. Suppose every molecule has decomposed and given rise to- two new molecules. Let's assume (for this purpose ) it requires negligible amount of energy for the molecule to decompose (or not any energy at all). So what will we observe? The amount...