Find the linear density of the wire when x=4m.

In summary, the author attempted to solve for the linear density of a wire when x=4m, but wasn't sure whether the answer was 3 or 4 kg/m3. However, after differentiation, it isclear that the answer is 4 kg/m3.
  • #1
The legend
422
0

Homework Statement



The mass of part of a wire is x(1+sqrt(x)) kilograms, where x
is measured in meters from one end of the wire. Find the
linear density of the wire when x=4m.



2. The attempt at a solution

Actually what i did was put in x = 4 in the mass equation given and divide by x since linear density = mass/length. And i get the answer to be 3.

But i don't know whether that's right or not.
Any help appreciated.
 
Physics news on Phys.org
  • #2


The legend said:

Homework Statement



The mass of part of a wire is x(1+sqrt(x)) kilograms, where x
is measured in meters from one end of the wire. Find the
linear density of the wire when x=4m.



2. The attempt at a solution

Actually what i did was put in x = 4 in the mass equation given and divide by x since linear density = mass/length. And i get the answer to be 3.

But i don't know whether that's right or not.
Any help appreciated.
The way I interpret the question is the expression x(1+sqrt(x)), gives you the mass at a point x, i.e. that at x=1 the mass is 2, at x=2 the mass is 2+2sqrt(2), etc. If that is the case, then your method wouldn't be correct. Instead, to get the total mass of the wire, what you need to do as sum over the contribution of each point on the wire. Can you think of any method that will do that for you?
 
  • #3


i would say it is integration that will help, but i haven't been taught that yet.
 
  • #4


The legend said:
i would say it is integration that will help, but i haven't been taught that yet.
Perhaps I am misinterpreting the question then.
 
  • #5
Hi Hoot! Hi The legend! :smile:

(have a square-root: √ :wink:)
The legend said:
The mass of part of a wire is x(1+sqrt(x)) kilograms, where x
is measured in meters from one end of the wire. Find the linear density of the wire when x=4m.

Isn't it differentiation?

I think they're saying that the total mass from 0 to x is x(1 + √x), and they want the density for a tiny bit round x = 4.
 
  • #6


Hootenanny said:
Perhaps I am misinterpreting the question then.

I took this sum from Stewart's book for calculus (Early Transcendentals 6th edition) and this sum was found under the chapter on derivatives(differentiation)...just to say

so how do I approach it then?
 
  • #7


The legend said:
I took this sum from Stewart's book for calculus (Early Transcendentals 6th edition) and this sum was found under the chapter on derivatives(differentiation)...just to say

so how do I approach it then?
If this is under differentiation, then I would suggest that tiny-tim has the correct interpretation. That is, the expression defines the mass of the segment of wire between 0 and x. In which case, the density is simply the rate of change of mass with respect to length.

P.S. Hi tim!
 
  • #8
Hi Hoot! :wink:

How's it goin'? :smile:
 
  • #9


tiny-tim said:
Hi Hoot! Hi The legend! :smile:

(have a square-root: √ :wink:)Isn't it differentiation?

I think they're saying that the total mass from 0 to x is x(1 + √x), and they want the density for a tiny bit round x = 4.

Hello tiny-tim! :smile:

But the question says that it is for a part of the wire.

The "mass of part" of a wire is x(1+sqrt(x)) kilograms,

But i did try it taking your way.
So what i did was this:

i differentiated the given mass function w.r.t length which gives

[tex]
\frac{dm}{dl} = 1 + \frac{3 \sqrt(x)}{2}
[/tex]
this is the linear density at any tiny little place. So what i did is I put in x=4 in the equation and got the answer to be 4 kg/m3
 
  • #10


...that took some editing there^...(latex)

is it right?
 
Last edited:
  • #11
Yup! 1 + 3√4/2 = 4 looks fine. :smile:
 
  • #12


thanks a lot! :approve:
 

Related to Find the linear density of the wire when x=4m.

1. What is the definition of linear density?

Linear density is the measure of mass per unit length of a one-dimensional object, such as a wire. It is usually represented by the symbol ρ (rho) and has units of kilograms per meter (kg/m).

2. How is linear density calculated?

Linear density is calculated by dividing the mass of the object by its length. In the case of a wire, the mass can be determined by weighing the wire, and the length can be measured using a ruler or tape measure.

3. How do you find the linear density of a wire at a specific point?

To find the linear density of a wire at a specific point, you need to know the mass and length of the wire at that point. Then, you can use the formula ρ = m / L, where ρ is the linear density, m is the mass, and L is the length.

4. Why is it important to find the linear density of a wire?

Finding the linear density of a wire is important because it allows us to determine the mass of a specific length of wire. This information is crucial in various fields, such as engineering, where the strength and durability of a wire may depend on its linear density.

5. How does the linear density of a wire change along its length?

The linear density of a wire is constant along its length, assuming the wire has a uniform mass distribution. This means that no matter where you measure along the wire, the linear density will remain the same.

Similar threads

  • Calculus and Beyond Homework Help
Replies
8
Views
1K
  • Calculus and Beyond Homework Help
Replies
14
Views
3K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
1K
  • Calculus and Beyond Homework Help
Replies
7
Views
859
  • Calculus and Beyond Homework Help
Replies
3
Views
3K
  • Calculus and Beyond Homework Help
Replies
3
Views
1K
  • Calculus and Beyond Homework Help
Replies
20
Views
512
  • Calculus and Beyond Homework Help
Replies
2
Views
1K
  • Calculus and Beyond Homework Help
Replies
6
Views
981
Back
Top