Measuring Definition and 1000 Threads

Hey, I am trying to measure and profile the density variation across a food wafer approximately 2 mm thick, I'm trying to find a method that will soley measure the density of the wafer and this method should be non destructive(the wafer can't be harmed). I have tried to do some research around...

Recently, I asked my physics teacher how to measure the height of a virtual image behind a concave mirror. He said he wasn't exactly sure so he offered to give extra credit to anyone who could find information on how to do it. Is there anyone who can help?

I'm trying to find the amount of repulsive force dark matter has on matter. To my understanding, the presence of dark matter is deduced from the fact that galaxies are being pushed away from one another instead of toward each other. The absence of matter between the galaxies suggests an...

hi... We generally use the Pythagoras formula for distance between two points in 2D, when the Cartesian co-ordinates are given... One directly extends it to 3D..having the distance going as \sqrt{x^{2}+y^{2}+z^{2}}... For a curved co-ordinate system, we have distances measured by...

Homework Statement Evening everybody. I am attempting to devise an experiment in order to measure the thermal diffusivity of ice and water. Imagine 3 brass plates, with water held between them, in approximately a 1mm gap (dx) by surface tension. The 3 plates have thermocouples between...

I just started learning some basic measure theory. Could someone explain the difference between \overline{F(A \times A)} and \overline{F(A) \times F(A)} where A is a finite set. Also, how would this be different in A was an countably infinite set? Thanks!

Part of my independant investigation requires me to carry out an experiment, which when I graph results, would confirm Malus' Law. I plan on using a bulb as my ambient source and two polarizing lenses. I will then measure the intensity of the light after polarization. Hopefully, if i graph...

Hi I was reading about the measurement of light years and was suprised to see it is the speed at which light goes through a vaacum. Is that because of the vaacum of space or does light have mass? thanks lneilson

Homework Statement Suppose E and B are measured by an ovserver at rest to be (in N/C) E = [0,0,60] B = [0,0,0] Now another observer travels close by in the +x direction at a constant speed of v = .8c with respect to the other observer. A. What is E' be in the moving frame? DONE b...

So the current through a diode as a function of applied voltage is: I = I0 [ exp( V q / KB T) - 1 ] where V is the voltage (independent variable), q is the charge of the electron (constant), T is temperature (constant over each trial), I0 is some parameter that's measured to be really tiny (I...

Hi there, Having a bit of trouble working something out for a lab experiment at uni - not sure if this really counts as a 'homework' question - but if it does, moderators, feel free to move it there! So we've got linearly polarised laser light hitting a quarter waveplate to create...

Warning: I have a minor grasp of physics... I am devising a study looking at the tension required in a surgical prosthesis (which is essentially a length of nylon with 80LB breaking strain) to produce stability between 2 bones. The nylon will be placed in a simple loop between 2 structures and...

So we did a dry lab in class, and we were determining sources of error for a particular lab dealing with the measurement of rate of reaction. My teacher said that the time intervals of the recorded concentration was too far apart (1 minute intervals). I was wondering if anyone would explain...

Homework Statement My question is. How would the acceleration vs. time graph look if an object was in free fall? I am referring here to the picket fence lab. The Attempt at a Solution My brain tells me, that it would be a horizontal line. But when I think about it, it doesn't...

If I wanted to determine the principle stresses on the surface of a circular tube could I use a 45deg planar rectangular rosette to measure the strains \epsilonx, \epsilony and \gammaxy? I only ask because on a flat surface the gauges could be oriented along the x-axis, the y-axis and 45 deg...

I am going to need to be experimentally measuring the stresses in a tubular steel frame. The tubular steel has a 0.75" OD and a thickness of 1/16". The frame is for a chair and I need to determine the stresses at various locations and determine whether or not the stress is below the endurance...

Hi everyone, http://img372.imageshack.us/img372/6093/img009h.jpg With the above, I really have no idea other than the standard s=d/t formula, but I doubt that has anything to do with it for a question worth 3 marks, and then looking at the two questions below, it'd make no sense. The...

I'm not using the template because this is a rather abstract question about the way to approach a scientific experiment. I'm beginning a science project in which I hope to define the speeds at which using an air conditioning unit becomes more efficient than rolling the windows down in a car...

I am developing a new chemical sensor. I want to test the sensitivity of the sensor to various chemicals such as K3Fe(CN)6 and Ascorbic Acid. My understanding was that you could use a chronoamperometry scan to do this measurement by injecting a controlled amount of chemical every 60 seconds...

I would like to put a cup of water in microwave and measure the temperature of the water as it rises with time in the microwave. Obviously electronic equipment will be fried in a microwave, but would it be possible to put a thermocouple in the water with its lead coming out of the microwave...

Is there a median sea level that the logs of sea level data is based? I know the moon causes the tides which upsets the equilibrium on a constant basis. I need this sea level to be based upon the distance from the center of the Earth so with the elevation of a particular city on the Planet...

Homework Statement Let's say you are given 10 identical springs. How would you develop a scale of force (i.e., a means of producing repeatable forces of variety of sizes) using these springs? Homework Equations None that I can think of. The Attempt at a Solution My guess is that...

Homework Statement Part A) Assume you have a capacitor with H-atom gas with a separation of the plates of {10}^{-4}meter and a voltage of 20 volts across the capacitor. Calculate the distance "d" (the displacement of the charges in the atom), where the induced dipole of the hydrogen atom...

In relativity example , a time measuring device is shown in which a ball moves up and down. This device is then placed in a moving frame and the motion of the ball is observed from the ground. To an observer on the ground, the path followed by the ball will be a slant line. And therefore when...

Homework Statement Given the following: • a battery, • a digital voltmeter (which records voltage as a function of time), • a digital ammeter (which records current as a function of time), • a battered industrial capacitor, • two copper plates, • and several bits of copper wire...

Hi, I'm trying to find out how changing the current fed through to a filament (e.g. sodium) of a lamp would change the light intensity. To determine the relationship, I will first need to find out how to measure the intensity of light. I've thought of one possible way to do it, but the...

Hi Everyone, This thread is a modified continuation of my "Digital Voltage Meter circuit " thread I started a long time ago here: https://www.physicsforums.com/showthread.php?t=180822 But with a few changes. In this case, I have a large DC capacitor that I want to monitor the voltage...

Hello All, This is a new thread related to my output stage setup. Only this time, rather than determining if something went wrong, I simply want to monitor the temperature of the MOSFET on the output stage. I have been doing a bit of research to see what kinds of sensors are available out there...

where do we use solid angle or steradian for measuring,in what way is theuseful over normal angle?

Hi All, A friend and I were recently considering the idea of measuring water flow in a fire hose, buy measuring the flux generated by the water moving through the hose. Neither of us are scientific by any means, but I've been trying to research the idea and have not gotten very far. I...

I have a project to measure young modulus by measuring the deflection of a beam under point mass. I have derived the equation but i am confused to how the end of beam should be placed to obtained best precision. Should it be both clamped end, freely supported end or a mixture of both? My idea...

If we cannot directly measure or observe C it doesn't mean C doesn't exist. If we can directly measure and observe A and B it always means A and B exists. Lets say it so happens that B becomes measurable and observable only and only when A and C somehow interacts and we don't know that. Let D...

Hi guys, I would like to know if any of you knows a method to determine the time it takes for a given substance to decompose. I would really like to perform such experiment, but I was not able to find anything, and I am sure this method exists, as everyone has already seen a table like this one...

Homework Statement Estimate the minimum length of time needed to measure the energy of a photon to an accuracy of 10^(-15) Joules. Homework Equations E = hv, where v is the frequency of the photon and h is Planck's constant in J*s Watts = Joules/second The Attempt at a Solution...

Homework Statement At an accident scene on a level road, investigators measure a car's skid mark to be 93m long. It was a rainy day and the coefficient of friction was estimated to be 0.32. Use these data to determine the speed of the car when the driver slammed on (and locked) the brakes...

Homework Statement You are a judge in a children's kite-flying contest, and two children will win prizes for the kites that pull most strongly and least strongly on their strings. To measure string tensions, you borrow a weight hanger, some slotted weights, and a protractor from your physics...

Tueseday, I go to Auburn to interview for an open position in Alabama Science in Motion. http://www.auburn.edu/academic/science_math/cosam/announcements/ Basically, I would be traveling around high schools, moving equipment, doing demonstrations, and developing new labs. I need to come...

Homework Statement At your disposal are a scale and a measuring tape. You are not allowed to jump on the scale. How would you go about measuring the average power you exert on the floor?Homework Equations P_{average}=\frac{\Delta E_{tot}}{\Delta t}The Attempt at a Solution I am honestly lost...

Hey, I'm trying to build a stroboscope for measuring the RPM of a few different fans. So far I've tried using LEDs but haven't been very successful. I tried using a function generator with square pulses (I tried both 20% duty cycle and 50%). So I started at 1 Hz and kept on increasing the...

How does one go about measuring the curvature of an object? Is there a way to uniquely represent a geometry if it follows an arbitrary curvature? I'm not even sure if I'm asking the right question, so here's why I want to know. I want to start modeling things in Solidworks to get a feel for...

I have to measure gravitational acceleration, and calculate my rate of error. The experiment i came up with is: a thick plastic tube, with no air inside, on the top side some sort of release mechanism, then have two motion detctors, 1M apart from each other, hooked up to a stopwatch to measure...

Please ignore the periods in the diagram as it won't allow me to properly draw it otherwise. I have an object, attached to a string, rotating uniformly in a circle but at an angle to the horizontal plane. It is going at 80RPM (so relatively slow). How would one go about measuring the length...

Hi. I'm trying to measure the milliseconds of duration of output from a little piezo speaker that is on a circuit (a freezer control unit). I tried connecting an oscilloscope across its leads, but when I apply power, I hear this resonating noise which does not sound healthy. This is only when...

A one liter cylinder is filled with 0.1 mm steel beads and the void volume is measured. A one liter cylinder is filled with 1 mm steel beads and the void volume is measured. A one liter cylinder is filled with 10 mm steel beads and the void volume is measured. Which bead size has the greatest...

Hi Everyone, First post here. I'm a 37 year old man who has just recently begun dabbling in the basics of Physics, purely for the academic enjoyment of making by brain go "ow!". Upon reading the "bowling ball on a bed sheet" description of how the gravity of large objects can bend the...

Hi, We have an assignment in my physics class and I am not sure where to start. We are suppose to duplicate Galileo's experiment, using the concept of similar triangles to calculate the height of the object. 1. What is the height of the three objects on the moon in miles? 2. What are the names...

So we had a thread about the FQXi essay contest a couple weeks back, and when I first saw the winners list this one... ...jumped out at me, both because the inclusion of the word "undecidability" indicated the paper might actually touch on matters (i.e. formal logic) I feel qualified to...

Has the permeability and permittivity of vacuum ever been measured in a vacuum or space?

What the title implies, with the discovery that the universe is expanding, are we observing the systems becoming harder to see? You'd think that with the speed of the objects and the distances involved, things like brightness and actual size would be getting reduced...

Suppose I'm alive and well and living in the 17th century and I want to make observations of times when Jupiter's moon Io disappears behind Jupiter. The best way to do this is to use the regular motion of the stars in the sky as a clock? What kind of accuracy could the best equipment of my day...