Uncertainties Definition and 152 Threads

Homework Statement Dear All, Suppose I had to values: A (±a) and B (±b) where A not equal to a and B not equal to b. I have to find the product of A and B taking into consideration uncertainties. Homework Equations A (±a) * B (±b) = C (±c) where c = (a/A+b/B) The Attempt at a...

I am processing the data in my pulley experiment and I have a doubt. I am measuring the efficiency, thus, I measured the work I inputed in the system. For when the mass being lifted by me was moved by 0.05m, I exerted a 1.4 N force and I had to exert that force for 0.275, 0.28, 0.285. (Those...

Turns out there is a problem with the question. Thanks though.

Hi, This problem has been bugging me for while. I hope someone can explain it. 1) If I measure something with a digital device and I know that the reading is correct, my only uncertainty is the limited significant figures displayed by the device. So if it read 24.6 the actual value...

Homework Statement The graph below shows the potential (V) applied to, and the current I(mA) drawn by, an electrical circuit. Use the max and min slope method to determine the: a) equation of line of best fit of the graph below (answer must be and equation relating to V and I). Your answers...

Homework Statement I am having trouble determining the error for a set of linear equations that represent a simple circuit with two voltage sources. I have found two possible uncertainties by solving using substitution, detailed below. The circuit is shown below...

I'm beginning to study control theory, and I keep reading about matched and unmatched uncertainties in the literature, but I have yet to find the definitions of matched and unmatched. Could someone explain it to me? Thanks.

I am confused over how to work with errors and uncertainties. So far when dealing with a small number of measurements I have used the partial derivative method to calculate the final error in my result e.g. if my result is E=mgh \text{ then assuming no error in g my uncertainty is }...

Homework Statement Find the number of moles: v = 10.00 +/- 0.03 cm3 c = 1.00 mol dm-3 Homework Equations n = cv The Attempt at a Solution When you are converted cm3 to dm3, do you need to also convert the uncertainty? When you finding n, and you are not given an uncertainty for...

Hi Ok, we all know that if a quantity T is measured N times, then all measurements have the same standard deviation (SD). Now, with this assumption one can derive the width of the average to get SD/sqrt(N). I have often encountered a dataset D, where each measurement has been assigned no...

Hi In http://sl-proj-bi-specification.web.cern.ch/sl-proj-bi-specification/Activities/Glossary/techglos.pdf it says that: ... if the sources of uncertainties are numerous, the Gaussian distribution is generally a good approximation. I don't quite understand why. The Central Limit Theorem (CLT)...

Hello, I am a newbie to these forums, so please be patient with me! OK, my first (but not only) problem is getting to understand Black Hole physics... I understand they (BHs) arise as solutions to the EFE's, and there are currently many efforts to tie in Quantum Theory in a consistent way which...

I have this question for homework and I'm well stuck! The specific heat capacity of a liquid was found by heating a measures quantity of the liquid for a certain length of time. The following results were obtained. Power of heater: ( 50.0 ± 0.5)W Mass of liquid: (200 ± 10)g Time of heating...

I have this question for homework and I'm well stuck! The specific heat capacity of a liquid was found by heating a measures quantity of the liquid for a certain length of time. The following results were obtained. Power of heater: ( 50.0 ± 0.5)W Mass of liquid: (200 ± 10)g Time of...

Can someone show me how to add, subtract, multiply and divide uncertainties in measurement.

Homework Statement A proton in a tin nucleus is known to lie within a sphere whose diameter is about 2.2 multiplied by 10E-14 m. What are the uncertainties in the momentum and kinetic energy of the proton? Homework Equations delta(x)*delta(p) >= hbar delta(E)*delta(t) >= hbar The...

Greetings, In trying to even ask this question it’s obvious I don’t understand enough about the topic of QM and light. Here is my attempt at my question: If I shine a laser beam at a target or sensor – the electronics every time detects the beam. How do the Schrodinger wave equation...

Homework Statement Determine the relationship between ^m/m and ^g/g from the relationship, m= 4pi^2/g ^= uncertainty Homework Equations m= 4pi^2/gThe Attempt at a Solution ^m/m = 4^g/g?

Hey :-) I want to establish the uncertainty in my fitted model to my data I can evaluate the variance for the predicted model, but I'm getting very confused as to how the variance can then give me the uncertainty in my model :S I know that the standard error of the mean may be taken as the...

erm, ok let's say i have a value, with uncertainty, like y = 10 ± 3 so let's say i multiply y by 2, then it becomes 20 but does the uncertainty becomes 3 x 2 = 6? , hence y = 20±6 ? what about divide? does it becomes 1.5? i roughly understand fractional uncertainty and propagation...

Homework Statement Calculate the density p and its uncertainty \Deltap showing all working Mass M (kg) 0.0163 \Delta{M} (kg) ? Diameter D (m) 0.014 \Delta{D} (m) ? Homework Equations \rho=MV p= \frac{6M}{\Pi{D}^3} Z=\frac{A^2B}{3C^{0.5}}...

Hi, I don´t know how this standard type uncertainty calculation can be solved. The situation is as follows: on a graph are three curves with different values, their slope is the speed of each car. The uncertainty of the y-axis (time) is 5%. Now the problem is that i want to display the values...

Why is it that if you have two data points a \pm b and c \pm d whose uncertainties are symmetrically distributed, the sum of the points is a+c \pm \sqrt{b^2+d^2} Can someone please help me with this derivation. Also, another separate question, suppose I have many uncertain data...

Homework Statement I'm doing a physics lab and need to do the uncertainties, and the method I'm using is the natural log method, hich goes like this: (equation used was k*(x^a)*(y^b)*(z^c) ) http://img297.imageshack.us/img297/3663/lnform.jpg The equation I'm doing...

Q=mcT, variables with uncertainties are m and T. If it were only Q=mT, the %uncertainty of Q would be %uncertainty of m + % uncertainty of T. But c=constant (no uncertainties), so what is the uncertainty of Q when Q=mcT? Do you just multiply the constant to the %uncertainties of m and T...

Hello fellow physicists :) I have recently done an experiment and am trying to propagate the uncertainty. Unfortuantely, I haven't done that in years, and need to remember how its done. For example: When theta= 20 (+-2) I want to find sin20 and the uncertainty: sin20=0.34 (+-?) How can I...

Homework Statement A glider moves on a level (horizontal) air track. The motion detector records five velocities of the glider: 0.48 m/s, 0.48 m/s, 0.53 m/s, 0.48 m/s, 0.47 m/s. The average velocity, uncertainty in the velocity, and relative uncertainty are Homework Equations Avg...

I am a First year Physics Student going into Second Year in a few weeks. I've been coping very well with all the work and theory. However Along with tight and Limited Lab schedule my sessions feel rushed and unfurfilling, particularly the analysis section. Although we are given a lab manual...

Calculating uncertainties, using calculus. What do these letters represent?? Homework Statement I think I've forgotten some basic calculus. Please help, this is reeally easy and quick answer for someone who know this, but its taking me forever to figure out. I attached document that I am...

Homework Statement I am unsure how to do uncertainties for my lab experiment. For example, we are suppose to estimate or guess the uncertainty for like the time and measurements.. Is there any general rule for proper guessing? Then I am unsure on what to do with the uncertainties in math...

Homework Statement When doing operations with numbers with uncertainties, if the significant figures of the resultant number's uncertainty is lower the significant figures of the resultant number, how should I show the resultant uncertainty. For example, Homework Equations if you do the...

1. Homework Statement For uncorrelated uncertainties LaTeX Code: \\delta x and LaTeX Code: \\delta y give the values and uncertainties for W in standard format. A.) W=x+y with x=4.2(0.2) and y=0.7(0.1) 2. Homework Equations [b]3. The Attempt at a Solution well i think i am...

Hi all! I'm currently doing an experiment using a compound pendulum trying to determine the value of g. I have a problem with my uncertainties: Error in period T: The period is measured with the use of a photo-gate of accuracy +/- 0.0001s. For each height i did 20 measurements from which i...

Homework Statement 1. A cylindrical can with radius of 3.1 +/- 0.4 cm and height 4.5 +/- 0.5 cm. What is the uncertainty in volume in cm cubed? 2. If theta= 0.40 +/- 0.02 radians, what is the uncertainty of y = tan (theta)? Homework Equations Volume of cylinder = Pie * r^2 * h...

Here's my value: length: 8.25 +/- 0.05cm If I convert 8.25 to m how to I .. convert my uncertainty?

Homework Statement Given that f=\frac{\bar u \bar v}{\bar u +\bar v} show that e_f=f^2({\frac{e_u}{\bar u^2} + \frac{e_v}{\bar v^2}) where e refers to the error. ok so I added up the fractional uncertainties Homework Equations The Attempt at a Solution and I got this...

(First post. Go easy on me, mods :D) EDIT: Seems I got the wrong forum. If a mod could be so kind to move it, I'd appreciate it :P Hi everyone! I'm working on a formal lab report for my physics class, and after propagating my uncertainties into a formula, I got an even smaller uncertainty...

Homework Statement So basically I'm supposed to calculate final velocity given time, displacement, and initial velocity. The only problem is that I'm supposed to find these results with uncertainties included. I know the how to do basic calculations with uncertainties I'm just confused when...

Homework Statement Basically I'm doing a lab and it states that I am not to omit uncertainties from my calculations. It has been ages since I've calculated with uncertainties so when I went back to my notes, they weren't there! Now I am completely lost and clueless. I know there are such...

Hello, first of all sorry for my bad english it is not my mother tongue I am new to the uncertainty and significant figures concept and I have measured some things, I want to write the results using them. The length of my table is 273,3 cm. The instrumental uncertainty is ± 0,3 cm, and I...

i need to know the formula for calculating the uncertainty of a gradient from a graph. the gradient is being used to calculate the moment of inertia but i can't calculate the error in my I cause i don't know how to calculate the error in my M! when i did the experiment, i assumed the error to...

I've been studying absolute uncertainties and do not understand any of it. If someone can explain it will really help. Especially with uncertainties including diameters and area.

For the following calculation, would the uncertainty propagate as I have estimated? \frac{\left(a \pm \Delta a \right) + \left(b \pm \Delta b \right)}{\left(c \pm \Delta c \right) \cdot \left(d \pm \Delta d \right)} = \frac{a+b}{cd} \pm \frac{a+b}{cd} \left( \frac{\Delta a + \Delta b}{a +...

Homework Statement If the uncertainty in a measurement of dameter is +-0.02cm is the uncertainty in radius the same or half of this value. The formula given in wikipedia implies that it would be half of the value. Cheers Homework Equations The Attempt at a Solution

My problem in short: I have a set of data, and I want to calculate the linear regression, and the uncertainty of the slope of the linear regression line, based on the uncertainties of the variables My problem in detail: My data is from an experiment and the uncertainties (errors) are...

If an average of three numbers with equal uncertainties is taken, does the average have an uncertainty of the sum of the absolute uncertainties of the three numbers? e.g. (3.0 +/- 0.1) + (6.0 +/- 0.1) + (9.0 +/- 0.1)/3 = 6.0 +/- 0.3? This makes sense to me because the three in the denominator...

I need to determine the propagation uncertainty of a calculated quantity (function of the variables mass, acceleration due to gravity, cap plate separation, and voltage), but I do not know the uncertainties of these measurements. I just know the values. What should I take the uncertainty to...

I'm so confused of the Heisenberg's Uncertainties... Here's a question i have to solve, although it looks very easy but my understanding of Heisenberg's Uncertainties is still shallow. Fuzzy a quantum mechanical duck lives in a world which h = 2 PI Js. Fuzzy has a mass of 2.0 kg and...

Hi guys, i am trying to work out the uncertainty of this equation Y = (AC-CX)/(B+X) and i am needed to work out the uncertainty in Y. values for these are: Y=2.18 UNCERTAINTY UNKNOWN A=29m Uncertainty in A denoted (Sa)=3mm B=710mm Uncertainty in B denoted(Sb)=3mm...