Units confusion in calculations

In summary: Hey PonderingMick, it looks like you got some great help and explanations from the community here! In summary, your initial calculation of kg x kg-2 does not equal kg, but rather kg-1 or 1/kg. This is because the units cancel out and leave 1/kg as the answer. Keep practicing and don't be afraid to ask for clarification or help when needed. The Physics Forums community is always happy to assist.
  • #1
PonderingMick
11
0
Can someone please explain how kg x kg-2 (in superscript) can equal kg?

I hope it does or my calc is wrong! Anywhere I can revise this kind of thing?

Mick
 
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  • #2
Welcome to PF!

Hi PonderingMick! Welcome to PF!

Same way that 10 x 10-2 = 10-1 :wink:

Why does that bother you? :smile:
 
  • #3


PonderingMick said:
Can someone please explain how kg x kg-2 (in superscript) can equal kg?

I hope it does or my calc is wrong! Anywhere I can revise this kind of thing?

Mick


tiny-tim said:
Hi PonderingMick! Welcome to PF!

Same way that 10 x 10-2 = 10-1 :wink:

Why does that bother you? :smile:

So the upshot is that kg x kg-2 doesn't equal kg.
 
  • #4
PonderingMick said:
Can someone please explain how kg x kg-2 (in superscript) can equal kg?

I hope it does or my calc is wrong! Anywhere I can revise this kind of thing?

Mick
Then, I am afraid, you calc is wrong.
[tex]kg \times kg^{-2}= kg^{-1}[/tex]
which is the same as
[tex]\frac{1}{kg}[/tex]
not kg.
 
  • #5
PonderingMick said:
Can someone please explain how kg x kg-2 (in superscript) can equal kg?

I hope it does or my calc is wrong! Anywhere I can revise this kind of thing?

Mick

Do you mean [tex]\frac{kg}{(kg)^2}[/tex]?

The answer would be:

[tex]\frac{1}{kg}[/tex], not [tex]kg[/tex]
 
  • #6
OK, I must be wrong before I get that far.

I have:

m x (ms-1)2
N m2 kg-2

So on the top I get:
m x m2s-2

and on the bottom I get

m kg s-2 m2 kg-2

all the m and the s cancel so i just get the kg left
 
  • #7
PonderingMick said:
OK, I must be wrong before I get that far.

I have:

m x (ms-1)2
N m2 kg-2

So on the top I get:
m x m2s-2

and on the bottom I get

m kg s-2 m2 kg-2

all the m and the s cancel so i just get the kg left

So what! You haven't even told us what the equation is so why should we care what the units are?

Actually it's not even an equation because it doesn't have an equals sign. How is anyone to know what is right or what is wrong with just one side of the equation?
 
  • #8
PonderingMick said:
OK, I must be wrong before I get that far.

I have:

m x (ms-1)2
N m2 kg-2

So on the top I get:
m x m2s-2

and on the bottom I get

m kg s-2 m2 kg-2

all the m and the s cancel so i just get the kg left

So you get
[tex]\frac{1}{kg^{-1}} = kg.[/tex]

Is that what you're supposed to get? Without knowing more details we can't say anything more than that the units of what you started with in this post work out to kg.
 
  • #9
Mute said:
So you get
[tex]\frac{1}{kg^{-1}} = kg.[/tex]

Is that what you're supposed to get? Without knowing more details we can't say anything more than that the units of what you started with in this post work out to kg.

Yes that's right, this means that my calculation is correct because the answer is a mass.

But I still don't understand why the answer to this is kg:

[tex]\frac{1}{kg^{-1}} = kg[/tex]
 
  • #10
Ok, I get it now:


[tex]\frac{1}{kg^{-1}} = kg[/tex]

for the same reason that
1
10-1 = 10

Thanks
 

FAQ: Units confusion in calculations

1. What is units confusion in calculations?

Units confusion in calculations refers to the incorrect use or mixing of different units of measurement in mathematical calculations. This can lead to errors and incorrect results.

2. How can units confusion affect scientific research?

Units confusion can significantly impact scientific research by producing inaccurate or unreliable data. It can also lead to difficulties in replicating experiments and hindering the progress of scientific knowledge.

3. What are some common examples of units confusion in calculations?

Some common examples of units confusion include mixing up metric and imperial units, using the wrong units for a specific variable, or forgetting to convert units when necessary.

4. How can scientists prevent units confusion in calculations?

To prevent units confusion, scientists should always double-check their calculations and ensure that all units are consistent and appropriate for the specific situation. It is also helpful to use unit conversion tables or calculator functions when necessary.

5. Can units confusion be avoided entirely?

While scientists can take steps to minimize units confusion, it may still occur in some cases. It is essential to be aware of the potential for units confusion and consistently check for errors to minimize its impact on calculations and research.

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