# Subtracting two vectors -- I'm not getting the right answer

• Aleksa
In summary, the problem involves finding the vector c by subtracting vector a from vector b, where vector a has a magnitude of 3 and is horizontal, and vector b has a magnitude of 3 and an angle of 120 degrees. The solution may involve using the Pythagorean theorem and finding the x and y components of each vector. The OP is requesting assistance in finding a solution.
Aleksa
Homework Statement
I have vector a=3 that is horizontal and vector b=3 with an angle of 120. They have same direction. I need to find c=b-a.
Relevant Equations
Pythagorean theorem
I added x and y-axis so it would be square, and then vector bx would be same as vector a, but a didn't get it right. I am out of ideas. Can you help me?

I'm not sure I understand your question. Could you post a diagram of your vectors ##\vec a## and ##\vec b## and your attempt to find ##\vec c##?

Aleksa said:
Homework Statement:: I have vector a=3 that is horizontal and vector b=3 with an angle of 120. They have same direction. I need to find c=b-a.
Relevant Equations:: Pythagorean theorem

I added x and y-axis so it would be square, and then vector bx would be same as vector a, but a didn't get it right. I am out of ideas. Can you help me?
Welcome to PF.

What are the x and y components of each vector? What do you get when you do the vector subtraction component-wise? Please show your work. Thanks.

## 1. Why is the magnitude of my subtracted vector larger than the individual magnitudes of the two vectors?

When subtracting two vectors, the resulting magnitude is not always equal to the difference between the individual magnitudes. This is because vector subtraction takes into account the direction of the vectors, not just their magnitudes. If the two vectors are pointing in opposite directions, the resulting magnitude will be larger than the individual magnitudes.

## 2. How do I determine the direction of the resulting vector when subtracting two vectors?

The direction of the resulting vector is determined by the direction of the first vector and the direction of the second vector. To find the direction, draw a vector diagram and use the head-to-tail method. The resulting vector will point from the tail of the first vector to the head of the second vector.

## 3. Can I subtract two vectors with different dimensions?

No, vector subtraction can only be performed on vectors with the same dimensions. This means that the two vectors must have the same number of components, such as both being 2D or both being 3D. If the vectors have different dimensions, they cannot be subtracted.

## 4. Why am I getting a negative result when subtracting two vectors?

A negative result when subtracting two vectors means that the resulting vector is pointing in the opposite direction of the first vector. This can happen when the two vectors are pointing in the same direction, but one has a larger magnitude than the other. In this case, the resulting vector will have a negative magnitude and point in the opposite direction of the larger vector.

## 5. How do I know if I have correctly subtracted two vectors?

To check if you have correctly subtracted two vectors, you can use the parallelogram method or the head-to-tail method. If the resulting vector formed by the two methods is the same, then you have correctly subtracted the vectors. Additionally, you can use the Pythagorean theorem to calculate the magnitude of the resulting vector and compare it to the difference between the individual magnitudes. If they are equal, then you have correctly subtracted the vectors.

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