Vector addition

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Homework Statement


Three forces each of magnitude 1N act from one corner towards the other corner of a square there sum has a magnitude nearest to :



Homework Equations




The Attempt at a Solution


diagonal of a square is equal to √2 , the answer should be 3√2
 

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  • #2
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Homework Statement


Three forces each of magnitude 1N act from one corner towards the other corner of a square there sum has a magnitude nearest to :



Homework Equations




The Attempt at a Solution


diagonal of a square is equal to √2 , the answer should be 3√2
Let's see what your diagram looks like. Do you know how to resolve vectors into components so that the vectors can be summed vectorially?
 
  • #3
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Let's see what your diagram looks like. Do you know how to resolve vectors into components so that the vectors can be summed vectorially?
yes I know vector resolution, but I want a hint on how to picturize this question
 
  • #4
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yes I know vector resolution, but I want a hint on how to picturize this question
Try laying the square out so that the corner at which the forces are applied is the lower left corner, and this corner coincides with the origin of an x-y Cartesian coordinate system. What are the components of the three forces in the x direction and in the y direction?
 
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  • #5
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Try laying the square out so that the corner at which the forces are applied is the lower left corner, and this corner coincides with the origin of an x-y Cartesian coordinate system. What are the components of the three forces in the x direction and in the y direction?
the net force(x) is in the -x direction 3/√2 and the Fnet(y) is also 3/√2 in -y direction
 
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  • #6
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the net force(x) is in the -x direction 3/√2 and the Fnet(y) is also 3/√2 in -y direction
The question sounds like it is multiple choise, where you have not shown the choises. The correct answer might be very simple. Otherwise, you may still need to make a diagram and show details of your work. Which corner is "the other corner"? Are all the forces pointing in the same direction?

PS. Why do you think that the lay-out of the square effects the total magnitude of the force?
 
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  • #7
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The question sounds like it is multiple choise, where you have not shown the choises. The correct answer might be very simple. Otherwise, you may still need to make a diagram and show details of your work. Which corner is "the other corner"? Are all the forces pointing in the same direction?

PS. Why do you think that the lay-out of the square effects the total magnitude of the force?
you are right its a multiple choice questions
the options are
a: nearest to 3
b:nearest to 2
c: nearest to 1
d: nearest to 2.4
 
  • #9
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diagonal of a square is equal to √2 , the answer should be 3√2
First, the diagonal of a unit square is √2 in length, but that isn't relevant in this problem. If you draw the diagram as @Chestermiller suggested, all forces extend out from the lower left corner of the square. All three forces have a magnitude of 1, so the force toward the upper right corner of the square doesn't reach that corner point.
Second, you apparently have multiplied √2 by 3 to get your answer, but that is incorrect for two reasons -- the magnitude of each force is 1, not √2, and the resultant of a force is not simply the sum of the magnitudes.

the net force(x) is in the -x direction 3/√2 and the Fnet(y) is also 3/√2 in -y direction
No.
That's not what I get.
Nor do I.
 
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  • #10
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To expand on what Chestermiller said in post #4, draw your diagram with the lower left corner of the square at the origin, and with the three vectors extending from the origin toward the three other corners of the square. Label the endpoints of all three vectors. Note that the diagonal vector doesn't reach the corner opposite the origin. Add the three vectors using vector addition. The magnitude of the resultant vector is what you want to find.
 
  • #11
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To expand on what Chestermiller said in post #4, draw your diagram with the lower left corner of the square at the origin, and with the three vectors extending from the origin toward the three other corners of the square.
That is the situation that I first assumed. But the statement given is "from one corner towards the other corner of a square". If they all point in the same direction, the answer is simple and quite different.
We need to see a diagram of the vectors, where they start, and where they end. Or tell us that they all start at the same corner and point toward different corners.
 
  • #12
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What is the component of the diagonal force in the x direction? in the y direction?
 
  • #13
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But the statement given is "from one corner towards the other corner of a square". If they all point in the same direction, the answer is simple and quite different.
Yes. However, since a square has four corners, "other corner of a square" is unclear. Do the vectors all start from one point, and point to the opposite corner of the square?

We need to see a diagram of the vectors, where they start, and where they end. Or tell us that they all start at the same corner and point toward different corners.
Or at least a clear description of the problem.
 
  • #14
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First, the diagonal of a unit square is √2 in length, but that isn't relevant in this problem. If you draw the diagram as @Chestermiller suggested, all forces extend out from the lower left corner of the square. All three forces have a magnitude of 1, so the force toward the upper right corner of the square doesn't reach that corner point.
Second, you apparently have multiplied √2 by 3 to get your answer, but that is incorrect for two reasons -- the magnitude of each force is 1, not √2, and the resultant of a force is not simply the sum of the magnitudes.


No.
Nor do I.
you are right i made that mistake, but why it is not simply the sum of vector magnitudes, 3 ?
 
  • #15
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you are right i made that mistake, but why it is not simply the sum of vector magnitudes, 3 ?
Have they not taught you this in your course?
 
  • #16
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Have they not taught you this in your course?
i am just confused that why the corner to corner is diagonal why not the nearest corner could be the corner,


and if the force is like you said from left down corner and extends to right upward corner ,then why can't we just add three vectors and get the magnitude of 3.
 
  • #17
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you are right i made that mistake
We still don't have a clear description of the problem. Do the vectors all point in the same direction, or does each one point to a different corner of the square?

We can't give useful help if we don't know what the problem is.
 
  • #18
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We still don't have a clear description of the problem. Do the vectors all point in the same direction, or does each one point to a different corner of the square?

We can't give useful help if we don't know what the problem is.
actually i also wanted to know if the problem is correct or wrong, it is created by over physics proffesor
 
  • #19
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What have you learned in your course about how to add vectors having different magnitudes and directions to obtain their resultant?
 
  • #20
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actually i also wanted to know if the problem is correct or wrong, it is created by over physics proffesor
It depends on what the problem is.
From the original post:
Three forces each of magnitude 1N act from one corner towards the other corner of a square
As I already mentioned, the square has three other corners. Are the vectors pointing to different corners or are they all pointing toward the opposite corner?

These questions have different answers.
 
  • #21
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What have you learned in your course about how to add vectors having different magnitudes and directions to obtain their resultant?
yes, we have learnt vector addition by head to tail rule and by law of cosines.
 
  • #22
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It depends on what the problem is.
From the original post:
As I already mentioned, the square has three other corners. Are the vectors pointing to different corners or are they all pointing toward the opposite corner?

These questions have different answers.
This is the only description given and the answer is nearest to 2.4
 
  • #23
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yes, we have learnt vector addition by head to tail rule and by law of cosines.
What about resolving into components, and adding the components?
 
  • #24
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That answer 2.4 is only correct for the problem where all the vectors start at the same corner and each vector points to a different corner. Given that problem, can you get that answer?
 
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  • #25
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you are right i made that mistake, but why it is not simply the sum of vector magnitudes, 3 ?
3 is only correct if they all point in the same direction. any "zig-zagging" reduces the magnitude of the sum.
 
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