• Support PF! Buy your school textbooks, materials and every day products Here!

Finding the maximum/absolute error in calculating the density of a metal sample.

  • #1

Homework Statement



"You are measuring the density of a metal sample. You have determined that the mass of the sample is 63.8 grams, and your error in this result is plus or minus 0.1 g. The volume of the sample is 8.8 +/- 0.1 cm^3. What is the maximum error (in g/cm^3) in your measurement of the sample density? "

Homework Equations


density=mass/volume
For z = x/y:
δz/z = δx/x + δy/y


The Attempt at a Solution


Well, filling into the equation for δz/z and substituting this for δρ/ρ and solving for δρ:
δρ=ρ(δm/m + δv/v)
=(63.8g/8.8cm^3)(0.1g/63.8g + 0.1cm^3/8.8cm^3)
=(7.25g/cm^3)(0.01293)
=0.0937g/cm^3


However, it says this answer is incorrect.
Any hints on where I am going wrong?
 

Answers and Replies

  • #2
115
2
Maybe it should be done in this way:
[tex]\rho_{max}=\frac{m+\Delta m}{V-\Delta V}\\
\rho_{min}=\frac{m-\Delta m}{V+\Delta V}\\
\Delta\rho=max\left(\rho-\rho_{min},\rho_{max}-\rho\right)
[/tex]
 
Last edited:
  • #3
I'm not quite sure I understand that last equation..
 
  • #4
115
2
You choose larger of these two differences.
 
  • #5
ok thanks for the clarification but that still doesn't produce the correct answer. Thanks for your help though.
 
  • #6
115
2
What is the correct answer?
 

Related Threads on Finding the maximum/absolute error in calculating the density of a metal sample.

  • Last Post
Replies
1
Views
906
Replies
4
Views
599
Replies
1
Views
6K
Replies
3
Views
4K
  • Last Post
Replies
2
Views
894
  • Last Post
Replies
18
Views
2K
  • Last Post
Replies
9
Views
1K
Replies
1
Views
1K
Replies
2
Views
8K
Top