Do I always have to convert to SI units?

In summary, when trying to calculate the minimum mass of a star using the formula M=PV³/2πG and given values of V=400km s^-1 and P=34.4 hours, it is best to stick with SI units for consistency. This includes using consistent units for the value of G. When in doubt, it is safest and quickest to stick with SI units for all quantities.
  • #1
Bugsy23
25
0
Hi, I'm trying to calculate the minimum mass of a star, where
M=PV³/2πG

The values I've been given are V=400km s^-1 and P=34.4 hours.

Does this mean that I have to convert these values to SI units, i.e. give the values in terms of metres and seconds rather than km and hours? This would obviously give a very different answer so I'm not sure
 
Mathematics news on Phys.org
  • #2
Bugsy23 said:
Hi, I'm trying to calculate the minimum mass of a star, where
M=PV³/2πG

The values I've been given are V=400km s^-1 and P=34.4 hours.

Does this mean that I have to convert these values to SI units, i.e. give the values in terms of metres and seconds rather than km and hours? This would obviously give a very different answer so I'm not sure
I would say that if you are given units in km and hrs, it makes sense to keep things in those units, not switch to meters and seconds.
 
  • #3
Mark44 said:
I would say that if you are given units in km and hrs, it makes sense to keep things in those units, not switch to meters and seconds.

Assuming that any constants are also in those units -in this case you also have G
 
  • #4
If you solve both numerically and with the units, you may also get factors of 3600 s h-1 floating around, so I'd suggest ensuring compatibility there.
 
  • #5
In other words, just be consistent in your use of units- if part of your problem has measurements in "miles" and "hours" and another in "meters" and "seconds", convert to one or the other.

Does it matter which you use? Yes, if your teacher says so!
 
  • #6
Bugsy23 said:
Hi, I'm trying to calculate the minimum mass of a star, where
M=PV³/2πG

The values I've been given are V=400km s^-1 and P=34.4 hours.

Does this mean that I have to convert these values to SI units, i.e. give the values in terms of metres and seconds rather than km and hours? This would obviously give a very different answer so I'm not sure

I think as a general rule it's always safest and quickest to stick to SI.
 
  • #7
Bugsy23 said:
...M=PV³/2πG...

...Does this mean that I have to convert these values to SI units,...
It really depends what units you are using for G. The other quantities' units should be consistent with that.

Dadface said:
I think as a general rule it's always safest and quickest to stick to SI.
Agreed, when in doubt go with SI units for everything.
 

1. Why is it important to convert to SI units?

SI units, also known as the International System of Units, are a globally accepted system of measurement used in scientific research and communication. Using SI units allows for consistency and accuracy in measurements, which is crucial in conducting experiments and sharing results with other scientists.

2. When do I need to convert to SI units?

You should always convert to SI units when conducting scientific experiments or communicating results. This ensures that your data is consistent and can be easily understood by other scientists around the world.

3. Can I use non-SI units in my research?

While it is generally recommended to use SI units in scientific research, non-SI units can be used if they are more appropriate for a specific measurement. However, it is important to clearly state the conversion to SI units in your data and results.

4. How do I convert to SI units?

To convert to SI units, you can use conversion factors or equations specific to the type of measurement you are working with. There are also many online conversion calculators available for easy conversion.

5. Are there any exceptions to converting to SI units?

In some cases, there may be exceptions to converting to SI units. For example, certain historical or cultural measurements may still be used in specific fields of study. However, it is always best to check with your peers or consult scientific literature to ensure the accuracy and consistency of your data.

Similar threads

I Dimension of an Angle: Clarifying the SI Standard
    • General Math
Replies
1
Views
1K
What SI Gear Standards Do You Use?
    • Mechanical Engineering
Replies
8
Views
2K
I How to Convert Cgs to SI Units for Flux and Energy Values?
    • Other Physics Topics
Replies
3
Views
2K
Stargazing What is an arcsec and how do I convert it into AU or m?
    • Astronomy and Astrophysics
Replies
8
Views
447
Help with Thermodynamics process equations and units
    • Introductory Physics Homework Help
Replies
11
Views
820
I Converting Unit Cell Volumes of Minerals to Density
    • Atomic and Condensed Matter
Replies
3
Views
1K
I How do I convert mass units in physics?
    • Other Physics Topics
Replies
2
Views
1K
I Time Measurement in Extremely Curved Space Regions
    • Special and General Relativity
3
Replies
95
Views
4K
Three Phase Per Unit System - Mark up, represent as single phase equiv
    • Introductory Physics Homework Help
Replies
1
Views
542
Converting equations in Natural units to SI?
    • Other Physics Topics
Replies
4
Views
7K

Hot Threads

Recent Insights

Back
Top