Hard Definition and 1000 Threads

Do you have hard water? Do you use a filtration system? I get a lot of build up on the faucet and on glass dishes that sit out for a while with water in them (like the cat's 2nd water dish that I don't change every day). Can hard water cause kidney stones or other health problems?

[b]1. E=hf "find the energy level of light with a frequency of 4.3 x 10 so the 14th jules [b]2. E=hf [b]3. Have no clue, tried multiplying Plancks constant by frequency but idk if its right

I need some general information about hard coatings and their basic oxides, but I cannot find any good links... Is it possible that you could know a link or two?

I'm new here and this is my first post, so I'ld like to give you all a hearty hello right at the beginning! Long story short, I'm in high-school and I'm wondering whether I should go nuts and take part of every single competition and olympiade etc to impress the universities I wish to apply for...

Hi all, have been wondering, why is it that when you put your hand in water, it's soft and there is hardly any resistance, but when you jump into it like from 100m above, you will most probably kill yourself? Is it because there is not enough time for the forces to distribute across the water...

Hi! I´m a senior high school student and I´m doing a school project about the conservation laws. I enjoy physics very much and I come asking you for advice. This is not a homework question. After doing most of my work for the school project, I´ve been told that you can get a deeper knowledge...

Which disciplines would you call "Hard Sciences" vs. "Soft Sciences"? As you all know, from time to time people will say there are the soft and hard sciences. Although it's not always clear where the distinctions are, it's generally believed they are there. For the poll, please rate these...

Homework Statement See picture for clarity. There are 2 infinite wires carrying a current i, one wire does it in the upward direction and the other wire in the downward direction. They are separated by a distance L+2d. Between them lies a circuit such that the part that moves with a velocity v...

I recently installed a new hard drive as my old one was damaged. I couldn't retrieve anything from my old hard drive so I had lost some items of software (for example, I had to buy a new webcam as I no longer had the driver for my old one). However, for some reason my speakers do not work with...

What do you like to do to wind down? Let me set the scene. You have arrived home after work/class. Do you hit the books with a vengeance or do you play video games all night?

Homework Statement I'm struggling with this question here from my QM class. I have read all my material on Spin (both Griffiths, and a chapter in an Icelandic book). I'we done some problems, but I really have no Idea where to start with this one. It goes something like this: Two particles...

Homework Statement What is the lattice energy of KI? Given the information below. Heat of formation for KI = -328 kJ/mol Heat of sublimation for K = 89.20 kJ/mol Ionization energy for K = 419 kJ/mol Bond dissociation energy for I2 = 149 kJ/mol Electron affinity for I = - 295...

Homework Statement Design an experiment to determine the temperature outside. Materials: 2 blocks of wood stop watch Measuring tape The Attempt at a Solution I believe it has something to do with measuring the rate of flow of a viscous liquid down a ramp. The colder the...

Well it's very hard for me anyway! In both of the following expressions I have to make x the subject. Can anybody break them down for me and explain step by step how to solve them? 1. ax/b + cx/d = e 2. a/bx + c/d = e From looking at the answers I know that the solutions are as...

Can some one get smart in physics by hard working? What do you think? Have a nice day!

My wife's computer hard drive failed the other day. She backed up her data, but on a partition on the same drive. The failure was mechanical, the spindle motor froze up. So accessing the backup partition was also out of the question. I was afraid we were doomed, but I read about people who...

Hard problemT_T Charge on capacitor?? Homework Statement A 6.0 uF capacitor is charged up to 12V and subsequently connected through a witch to a 100ohm resistor. At t=0, the switch is closed. What's the charge on the capacitor 6.0ms(=.0006sec which is RC) after the switch is closed...

Homework Statement A line corresponding to light of the wavelength 519.8 nm is observed at an angle 12 degrees in the second-order spectrum of a diffraction grating. The grating is 1 cm in width, what is the line spacing of the grating? how many per centimetre? what is the lowest order...

original link: http://www.maths.cam.ac.uk/teaching/pastpapers/2001/Part_IA/PaperIA_2.pdf" Question 11F Dipkomsky, a desperado in the wild West, is surrounded by an enemy gang and fighting tooth and nail for his survival. He has m guns, m > 1, pointing in different directions and tries...

Homework Statement http://img163.imageshack.us/img163/7010/78614537.jpg o= student The position of the teacher is (d) from the mirror. mirror is 6m a) Calculate the maximum distance(d) of the corridor from the mirror b) Trace the diagram. Draw the ray diagram to support your calculation...

Homework Statement Prove that the product of two (nxn) non-singular matrixes A and B is non singular and that (AB)^{-1} = B^{-1}A^{-1} Homework Equations The Attempt at a Solution Well AI = A^{-1) we could perhaps try asing AA^{-1} and BB^{-1} ?? Hopeless. What type of...

Hi, In this other thread https://www.physicsforums.com/showthread.php?t=354424" I was hoping to get a scientific answer to my question. Apparently this was not an easy question or hypothesis that was easily falsified. I was sorry to see the subject turned into a unpleasant debate which ended up...

I have one test and i need to study classical mechanics , electromagnetism , statistical mechanics and quantum mechanics, anyone have some tips for maximize the time ??

My 1 TB external hard drive which currently houses about 850 gbs worth of media is having an issue. It won't display in my computer but it displays in disk management in black as 931 gb of unalloacted space. When I right click I can't assign it to a drive letter. When disk management pops...

I've heard from PhdComics, a fair few members here, and from a person I know that's not from the internets that becoming a professor is basically impossible. I have a hard time believing this. It seems to me that if you get a PhD at a decent university, did a legitimate thesis, and found a...

Homework Statement the motion of a particle of mass m=10kg is described by the equation x= y= where x and y are in meters and t in seconds. Determine the velocity acceleration of the particle and the force acting on it. Homework Equations The Attempt at a Solution

go to an average 4 year college like the University of Santa Barbara , and have grades of C and just a few A's or B's , as opposed to if you have all A's and are going to Berkley ? Really curious about how employers view grades and what school you went to in making a hiring decision

Okay, here goes. The first one to figure it out will receive an HTML code in their email address (please give me yours when you answer) that is a virtual pet.:smile: Good luck! *** A man is coming from Switzerland on a train after his successful eye surgery. His eyesight was still poor, so if...

OK, this is really confusing me. Mostly because i suck at spatial stuff. If the gradient vector at a given point points in the direction in which a function is increasing, then how can it be perpendicular to the tangent plane at that point? If it's perpendicular to the tangent plane...

physics! Science! Really Hard how does friction affect how far an object will roll

Homework Statement so a block of mass m slides on a frictionless surface of an inclined plane of angle theta which itself has mass M and can slide on a horizontal surface. Assuming no friction, find the accel of the block and the inclined plane.. The Attempt at a Solution well...

I am a mechanical engineer currently working in design at a semiconductor/data-storage process equipment company. I've come to learn that I am better at analysis than i am at design. I like using and gathering data and developing specifications, whereas mechanical design requires a kind of...

Homework Statement hi there, I am having some trouble with my physics homework and i was wondering if anyone can help me. i have no clue what to do. these are the questions 1. what does the slope of the graph "maximum force of static friction vs normal force" mean? (maximum force of...

Very Hard Projectile Motion making me nuts<Help, Urgent!> Hey there, i am in grade 12 4u physics course and i would really appreciate it if someone can help me out with the following Projectile Motion questions. I tried to figure out how to do it but i can't think of any. Question:1...

If G is a connected graph with a cut-vertex v and G1 is a component of G-v, then show that the induced subgraph <V(G1)U{v}> of G need NOT be a block of G. I guess all I would need is a counterexample, but I can't come up with one.

Homework Statement a pendulum of mass m and length L is pulled back an angle θ and released. After the pendulum swings through its lowest point, it encounters a peg α degrees out and r meters from the top of the string. The mass swings up about the peg until the string becomes slack with the...

Homework Statement ((e^{iz})/((1+z²))) Find a Laurent expansion valid for 0<|z-i|<1and use it to show that the derivative will leave you with the residue a₋₁. So we have an annulus with its center at one of the singularities. Since the other singularity at z=-i is outside...

Hard Kinematics Question- Please Help! Homework Statement When placing traffic lights at an intersections, planners have to determine how long the yellow light should stay on. This will depend on the speed limit on the road and on the length of the intersection. Outside a building,on the...

Hi all, A friend of mine asked me if i had any ideas about the following problem, i tackled it but with no success, so i thought i would post it here. It is not a homework problem, or a regular textbook problem. Problem: If we know that a series with positive terms ...

I am designing a component (Cam Driver) that has 2 features. One feature that acts as a cam, it slides against another component with heavy surface stress to move the other component. The 2nd feature of this Cam Driver is a threaded rod that mates with a piston in a pneumatic cylinder, thus...

The last time I defragged a hard drive was on my desktop computer with windows vista. My laptop seems to be slowing down slightly, I was hoping to defrag it, as it has not been for a very long time. I don't know where to go to access this feature in windows XP. I use "search" in the start bar...

1. How can something travel faster than light? 2. You have two identical bars of iron – except that one is a magnet. Without using any piece of apparatus, or any other object, how can you find out which is which? Hope you can help Thankyou :)

Homework Statement Does there exist a continuous function f: R -> R such that f'(f(x)) = x ? Homework Equations The Attempt at a Solution I was trying to find an example, but wasn't able to, and if I had to take a guess whether such a function exists or not, I'd say no. Here...

Homework Statement Help, I don't know how to do the following question: Using Laplace to solve x' -y =1 2x' +x +y' = (t2-2t+1)e-(t-1) Homework Equations x(1)=0 y(3)=0 The Attempt at a Solution The problem I'm having is the initial conditions aren't at zero, and I'm not sure...

How would you integrate this. I tried all integration methods available in Calculus II to no avail. ∫√(1+sin x) dx

Homework Statement A ball player hits a home run, and the baseball just clears a wall 8.00 m high located 122.5 m from home plate. The ball is hit at an angle of 39.9◦ to the horizontal, and air resistance is negligible. Assume the ball is hit at a height of 1.2 m above the ground...

Homework Statement Prove that sin(5A)+sin(2A)-sin(A) = sin(2A)*(2*cos(3A)+1)Homework Equations sin(2A) = 2(sin(A)cos(A)) cos(2B) = cos2(A)-sin2(A) cos(A+B) = cos(A)cos(B) - sin(A)sin(B) sin(A+B) = sin(A)cos(B) + sin(B)cos(A) The Attempt at a Solution I can't find any other way than to just...

Inspired by the recent thread on flying coffee grains I felt the urge to ask if anyone knows why coffee is so darn hard to clean up? It doesn't stick to the rag as most substances do. I'm assuming it has something to do with the grains' surface structure, but what kind of physics describes this?

A long time ago, I was once told that too much reliance on databases in programing can create slow programs. Databases provide a nice way to store and organize information but they may not retrieve and write information quickly. Clearly ram is the fastest way to access meomry but the size of ram...

I can't find a solution to these questions. Can someone help? 1. An algorithm to determine if a Sudoku puzzle is easy, medium, hard, or evil. 2. For every valid Sudoku puzzle, there exist at least one valid solution. True or false? Proof?