What is the Relationship Between Uncertainty in Diameter and Radius?

In summary, the uncertainty in the radius of a measurement is half of the uncertainty in the diameter, as implied by the formula given in Wikipedia. This can be seen by dividing the diameter by 2. When calculating the uncertainty in the volume of a sphere using the radius, the uncertainty will be larger, as shown by the formula deltaV/V = 3*deltaR/R.
  • #1
swain1
30
0

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

 
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  • #2
swain1 said:

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


Yes, it will be half of this value. If the uncertainty had been given in percent form, then the percent uncertainty on the radius and on the diameter would be the same.
 
  • #3
you should had this formula in your relevant equations thingy:
radius = diameter /2

2 is a number, and has uncertainty of 0
so, use division rule
 
  • #4
Ok thanks guys.
I now have to work out the uncertainty in the voume of a sphere using the radius I have. Any clues on how to get the uncertainty in this value? I would expect that it would be bigger but I can't really understand why?
 
  • #5
I have this formula

deltav/v=3xdeltar/r

Is this correct?
 

1. What is meant by "combining uncertainties"?

Combining uncertainties refers to the process of quantifying and taking into account the uncertainties associated with multiple variables in a scientific measurement or calculation. It involves considering the individual uncertainties of each variable and determining the overall uncertainty of the final result.

2. Why is it important to combine uncertainties?

Combining uncertainties is important because it allows for a more accurate and reliable representation of the final result. By taking into account the uncertainties of each variable, we can better understand the potential errors or variations in the measurement or calculation, and make more informed decisions based on the data.

3. What are some methods for combining uncertainties?

There are several methods for combining uncertainties, including the root-sum-square method, the Monte Carlo method, and the Bayesian method. Each method has its own advantages and is suitable for different types of uncertainties and data sets.

4. How do we express combined uncertainties?

Combined uncertainties are typically expressed using a plus or minus value, indicating the range of possible error in the final result. For example, if the final result is 10 +/- 0.2, this means that the true value could be anywhere between 9.8 and 10.2 due to the combined uncertainties.

5. What are some sources of uncertainties that can be combined?

Some common sources of uncertainties that can be combined include instrumental errors, human errors, statistical errors, and systematic errors. These uncertainties can arise from various factors such as limitations of the measuring instrument, variations in environmental conditions, and limitations of the experimental setup.

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