What is Uncertainty: Definition and 1000 Discussions
Uncertainty refers to epistemic situations involving imperfect or unknown information. It applies to predictions of future events, to physical measurements that are already made, or to the unknown. Uncertainty arises in partially observable or stochastic environments, as well as due to ignorance, indolence, or both. It arises in any number of fields, including insurance, philosophy, physics, statistics, economics, finance, psychology, sociology, engineering, metrology, meteorology, ecology and information science.
Homework Statement
The radius of a circle is measured to be 2.4 cm +/- 0.1 cm.
Find the error in the area of the circle.
Find the error in the circumference.
Homework Equations
Have no idea but I'm taking a guess it could be multiplying fractional uncertainties?
The Attempt at a...
Hello everyone, I've run into a little issue with physics homework. During a lab we recently had, we were required to measure the amount of time it took for a ball to drop from different heights (2m, 1.5m, etc) using a photogate. Now that I'm writing the lab report, I have to find the...
Homework Statement
1.0 micrometer diameter dust particles (m=1.0 * 10^-15 kg) are in a vacuum chamber. The dust particles are released from rest above a 1.0 micrometer diameter hole, fall through the hole, and land on a detector at distance d below.
Part A:
If the particles were purely...
What is Heisenberg's Uncertainty Principle??
Homework Statement
Hey everyone,
Until very recently, I had always thought that Heisenberg's uncertainty principle was that
\Delta x \Delta p \geq \frac{h}{2\pi} (or \hbar)
However, I'm doing my final year of high school physics this year...
Hi! I had a thought as to how leptons hold the properties attributed to them by Heisenberg and modern quantum mechanics.
It is my belief that the Uncertainty principle is caused only by the fact that the fast moving electrons distort space and time in their local fields. This may be accounted...
First:
If subatomic particles have momentum, then don't objects at rest have momentum [since they are made of these momentous particles] ?
My main question is:
If the position of an electron is uncertain, then isn't the position of an object NOT constant? Even to the slightest degree?
Thanks...
I am new, and I don't have a physics background, so please excuse the question if it is incredibly easy...
Does the Heisenberg Uncertainty Principle mean that we just can't measure the location of an electron to perfect accuracy, but such a location does exit (we just can't know what it is)...
Recently, I have a look of the Einstein's thought experiments challenging the uncertainty principle.
One of the experiments is the Einstein's slit.
I found the description about it :
"Consider a particle passing through a slit of width d. The slit introduces an uncertainty in momentum of...
I have often seen it stated that the Uncertainty Principle (UP) is a unique feature of Quantum Physics, but surely it applies classically too?
For example, if someone throws a ball across a room, and I take a photo with a shutter speed of 1 second, the resultant photo will tell me a lot about...
Homework Statement
I wrote a code that calculates pi using accept&reject monte carlo integration. It picks -1000000000 pseudo-random points (x,y), and counts the number of points that fall within a unit circle (let's call that number k).
The ratio of k/ N (N = Number of trials = 1000000000)...
(High-school level)
I got given some formulas today for calculating uncertainty of a value that has been square rooted, squared, inversed, inverse squared and inverse square rooted.
I'm not totally sure what they mean however, but I kinda have an idea.
Square root: y=x^1/2...
I've been watching Susskind's lectures on quantum mechanics and he mentions that the time taken for two electrons to entangle their spin is a function of their distance, which in itself determines the energy that is released when two electrons fall into a singlet state. Does anyone here know how...
Hey all, I'm a student curently studying in a Singaporean Junior College (American 12th grade equivalent). I was curious and just thought of the following:
Suppose a system with a electron and a proton nucleus, a hydrogen atom.
From electrostatic force and circular motion equations-
F =...
Homework Statement
This is about experimental physics. I have a value of resistance R=9000 \pm 1000. Then I had to do the following calculation:
\frac{40000}{9000}=4.44 \ \Omega
So, I'm not quite sure how to calculate the final uncertainty from my uncertainty \sigma = \pm 1 \ k\Omega...
So to determine the position of an object you can scatter light off of it. Fine. But then my textbook says you can't know the exact position of the object because of diffraction effects. We've covered the diffraction of light through narrow slits but I don't know why if you were scattering light...
I have been trying to figure out other pairs of variables in Heisenberg's uncertainty relationship apart from the well known position-momentum and time-energy pairs.
I am particularly interested in electric fireld strength and magnetic field strenght.
The reason for my interest is that if I...
Homework Statement
Heisenberg's uncertainty principle states that you cannot simultaneously know the position and momentum of an object. In this video link, a laser is aimed through a slot and projected onto a wall. As the slot gets narrower, the projection also gets narrower. Eventually...
Hey I'm hoping for some help in understanding the relationship between ##\delta x \delta p \geq h## and ##\delta k \delta x \approx 1##.
I know the second describes the relationship between span of a wave packet and the frequencies used in a series representation of a Gaussian function.
I...
Homework Statement
A neutron in an atomic nucleus is bound to other neutrons and protons in the nucleus by the strong nuclear force when it comes within about 1 fm of another particle . What is the approximate kinetic energy in MeV of a neutron that is localised to within such a region? Take...
I'm trying to write a lab report.
I've taken some measurements several times and have calculated the results and the systematic uncertainty for each set of measurements. i.e. I have x_{i} s, which are the results, and I have \Delta x_{i} s, which are the systematic uncertainties, calculated...
This is my first post here, and I just want to add the following disclaimers: I'm not in university, and I have never taken a physics class proper in my life. xD I want to say I understand quantum mechanics in principle, as while I think I understand many of the concepts I do not know it...
Is this explanation of uncertainty principle from wikipedia correct? Is this "compressing" the Fourier series/integral? Because the function is not periodic, and with infinite frequencies some of then would put make the speed greater than c
"According to the de Broglie hypothesis, every...
Homework Statement
I don't know how to do 13.10 and 13.11
http://a367.yahoofs.com/hkblog/LR5wVsiTBB9XH4KDYpBfXDI-_9/blog/20110511014559607.jpg?ib_____DMAbgW2U6
The Attempt at a Solution
I just can't get the answer.
Can you show me the details of the proof and the steps to the...
Hi,
(this is my first post! : D )
I'm a freshman in college. I came in wanting to major in physics and English.
I soon tossed english aside and immersed myself in the sciences(during like the first month). I took Physics 1(general overview course touched upon all topics of physics from...
It seems the book makes a mistake.
Uncertainty principle states: (Uncertainty of p) times (uncertainty of x)>=(a constant)
But in the following picture, the writer calculates the exact value of momentum and find uncertainty of x. Is it wrong?
I am using Understanding Physics written by...
Homework Statement
I quote from my text, "The decay of excited states in atoms and nuclei often leave the system in another, albeit lower-energy, excited state. (a) One example is the decay between two excited states of the nucleus of ^48Ti. The upper state has a lifetime of 1.4 ps, the...
Some people suggest that free will is proven by the heisenburg uncertainty principle, which states that you can not predict the outcome of a quantum event. Does this mean that humans can some how consciously tell every electron in their body how to act in order for their desires to be fulfilled...
Homework Statement
A particle is moving freely in the x direction.
Find the initially allowed (i.e. at t=0) values of \langle x^2 \rangle and \langle p^2 \rangle, and find equations of motion for \Delta x and \Delta p,
Homework Equations
\frac{d}{dt}\langle A\rangle =...
I have some data (4 runs each of about 10 trials) which is binomial with n_hits/N_trials
n/N = 0/11, 0/9, 0/10, 0/10
So, I estimate the probability p = n/N = 0
But how can I calculate an uncertainty on this value?
I thought to try
total N_tot=40 and n_tot=1, so p_tot=1/40 = 0.025
(i.e...
Warning: My understanding of physics is minimal let alone Quantum Mechanics so please excuse (but feel free to correct) my misunderstandings.
My understanding of the Uncertainty Principle is that because photons have to hit a particle so that we can view it, we can never be certain of...
Hi! I am Calculating the uncertainty in an Evaporation Rate i obtained from measurements around a lake using E=C.U(ess-ea)/P where C is constant 135mm/day at 1.5m above lake surface, U is average wind speed, P air pressure hPa, ess saturation vapour pressure @lake surface temp (Ave), ea is air...
Homework Statement
A small ball of mass 2.0×10−6 kg is dropped on a table from a height of 1.0 m. After each bounce the ball rises to 80 % of its height before the bounce because of its inelastic collision with the table.
Estimate how many bounces occur before the uncertainty principle...
Homework Statement
The relationship between resistance with temperature is expressed by the equation of R= R0[1+ α(T-T0)], where Ro is the resistance at the reference temp. T0 and α for the resistor material has been determined to be 0.0048 ± 0.1% oC. In the range 0 to 100* C, in which we...
Imagine humans had a size on the order of magnitude close to the size of a large planet. An electron, then, proportionality-wise, would roughly be the size of an apple. To us large-scale humans, the apple might seem quantum mechanical and unpredictable because it seems exceedingly tiny. But we...
Homework Statement
show that |\DeltaE/E| = |\Delta\lambda/\lambda|<<1
Homework Equations
\DeltaE>hbar/2pi\Deltat
\lambda=hc/E
The Attempt at a Solution
dunno where to start.
I think I undetstand the role of the uncertainty principle in explaining the existence of interference patterns in the double slit expt with electrons i.e. the slits reduce the uncertainty in position and consuequently there is a greater uncertainty in momentum which results in interference...
1. Homework Statement [/b]
1)for an object of size 0.5 Angstrom, what is the longest-wavelength photon with which it can be observed?
2)for the object of problem 1, what is the smallest-energy electron which can be used to make the measurement?
Homework Equations
1)\Deltap x \Delta x \geq...
Does the Uncertainty Principle apply to the calculation of particles in a past point in time?
As in, can we know the momentum and position of a particle in the past?
Lets say I measure the z-component of a particles angular momentum, then I can't know for certain the x and y componets. So if I measure the Z componet to be 0, the x and y componets could be zero or not.
So is it impossible to say that the particles total angular mometum is zero meaning...
Hydrogen Atom ---> Uncertainty Principle
Hey guys, I'm having some trouble with this one.
[PLAIN]http://img849.imageshack.us/img849/2039/physhw.jpg
How do I get started?
Homework Statement
In my lab we are doing Franck Hurtz experiment with heated mercury and electron beams. We already took data but i need a little help. I have the locations of the minimums A B C D and E, and each point has it's own uncertainty. a b c d and e. What i needed to find was the...
"THE STRANGE THEORY OF LIGHT AND MATTER " and uncertainty principle
In Feynman's QED: THE STRANGE THEORY OF LIGHT AND MATTER it is used one elementary QM formula W=h\nu. But it is not described principle of uncertainty, which is the second most important formula. Do you have any idea, how to...
Homework Statement
\phi(x) is in Schwartz space, and {\int|\phi(x)|^2dx=1.
I need to show that (\int_{R^n}|x|^2|\phi(x)|^2dx)(\int_{R^n}|\xi|^2|\phi(\xi)|^2d\xi)\geq \dfrac{n^2}{16\pi^2}Homework Equations
Heisenberg uncertainty in one dimension...
The aim of the investigation was to calculate, as accurately and precisely as possible, the internal resistance (r) and the Electromotive Force (EMF) of two cells; an AA Cell and a D Cell, both of which were rated to supply a voltage of 1.5V. I proceeded to do this by measuring the current of...
I'm trying to get my head round this. I don't see why our inability to measure the world around us means that at the quantum level things must be random. I understand that measuring momentum of a particle to a high degree of accuracy means losing accuracy in it known position. But I don't...
Uncertainty analysis in aerofoil! Help!
Homework Statement
Wind tunnel experiment using a constant velocity to determine Cl, Cd and Cm at different angle of attack (-5, 0, 5, 10, 15) of a symmetric airfoil. Error analysis of the experimental investigation to asses uncertainties in Cd, Cl, Cm...
]How can H.U.P be used to explain the following :
(i) The non-existence of the electron in the nucleus.
(ii) The existence of protons, neutrons and alpha particle.
(iii) The existence of finite zero point energy.
(iV) The binding energy of an electron in an Hydrogen atom is of the order of 15...
I had this https://www.physicsforums.com/showthread.php?p=3200140#post3200140", which I posted on PF. I got the answer, but then I started thinking more about it and have some theoretical questions.
If you did have this particle of mass m in a box of length L, which you are trying to stop...
How do time-energy uncertainty and special relativity's rules about observers seeing time different for each other interact?
Heisenberg's uncertainty principal applies to time and energy: a system existing for a short duration of time has more uncertainty in its energy than one that exists...
hello
I have some questions which I was struggeling with
1. Is percentage error the same as percentage uncertainty?
Because percentage error is a measurement of accuracy and is percentage uncertainty also a measure of accuracy?
2. How do percentage uncertainty and percentage difference affect...