What is Vectors: Definition and 1000 Discussions

In mathematics, physics and engineering, a Euclidean vector or simply a vector (sometimes called a geometric vector or spatial vector) is a geometric object that has magnitude (or length) and direction. Vectors can be added to other vectors according to vector algebra. A Euclidean vector is frequently represented by a ray (a directed line segment), or graphically as an arrow connecting an initial point A with a terminal point B, and denoted by






A
B






{\displaystyle {\overrightarrow {AB}}}
.A vector is what is needed to "carry" the point A to the point B; the Latin word vector means "carrier". It was first used by 18th century astronomers investigating planetary revolution around the Sun. The magnitude of the vector is the distance between the two points, and the direction refers to the direction of displacement from A to B. Many algebraic operations on real numbers such as addition, subtraction, multiplication, and negation have close analogues for vectors, operations which obey the familiar algebraic laws of commutativity, associativity, and distributivity. These operations and associated laws qualify Euclidean vectors as an example of the more generalized concept of vectors defined simply as elements of a vector space.
Vectors play an important role in physics: the velocity and acceleration of a moving object and the forces acting on it can all be described with vectors. Many other physical quantities can be usefully thought of as vectors. Although most of them do not represent distances (except, for example, position or displacement), their magnitude and direction can still be represented by the length and direction of an arrow. The mathematical representation of a physical vector depends on the coordinate system used to describe it. Other vector-like objects that describe physical quantities and transform in a similar way under changes of the coordinate system include pseudovectors and tensors.

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  1. G

    Find Vector \overrightarrow{B_1B} for Triangle ABC

    Homework Statement Given points of a triangle: A(4,1,-2),B(2,0,0),C(-2,3,-5). Line p contains point B, is orthogonal to \overline{AC}, and is coplanar with ABC. Intersection of p and \overline{AC} is the point B_1. Find vector \overrightarrow{B_1B}. Homework Equations -Vector projection - Dot...
  2. S

    I Original direction of force versus vector components

    What happens to a mechanical force's real original direction i.e. when we divide it into components of basis vectors, which in turn change as per problem at hand (like gravity components at inclined plane ), how we arrive at correct physics by taking two/three arbitrary directions of our choice...
  3. thegirl

    I Drawing a reciprocal lattice, also basis

    Hey could anyone please explain how you go about drawing a reciprocal lattice? For example a 2d rectangular lattice to it's reciprocal form? Also... I don't know if this is correct but if you have a 2d rectangular lattice with lattice vectors L=n1a1 + n2a2 would the reciprocal lattice vectors...
  4. TheMathNoob

    Find the equation of the line by using vectors

    Homework Statement I have to find the equation of the line by using any vector a and b in a way that the line fits the triangle generated by vector addition. If you don't understand my statement, look at my attached file. You will understand what I mean by triangle. Is my solution right...
  5. B

    Opposite Direction: S 20° W | Homework Help

    Homework Statement What would be the opposite direction of [E 20 degrees N}? Homework Equations No real equation The Attempt at a Solution Is the opposite direction [S 20 degrees W]?
  6. N

    Calculating the tangential and normal vectors of an ellipse

    Homework Statement The ellipse is given as (x^2/a^2) + (y^2/b^2)=1 I´m meant to calculate a tangential vector, a normal vector and find an equation for the tangent using a random point (x0,y0). I´m meant to do this in 2 ways: firstly by using the parametrization x(t)=a*cos(t) and...
  7. haruspex

    Insights Frequently Made Errors in Vectors - Elementary Use - Comments

    haruspex submitted a new PF Insights post Frequently Made Errors in Vectors - Elementary Use Continue reading the Original PF Insights Post.
  8. Ryan McCormick

    Vectors A + B: Are Any of the Above True?

    Homework Statement If magnitude (absolute value) of vectors ( A + B ) ^2 = A^2 + B^2 then: a) A and B must be parallel and in the same direction b) A and B must be parallel and in opposite directions c) it must be true that either A or B is zero d) the angle between A and B must be 60...
  9. Math Amateur

    Computations with Tangent Vectors and Pushforwards - Lee

    I am reading John M. Lee's book: Introduction to Smooth Manifolds ... I am focused on Chapter 3: Tangent Vectors ... I need some help in fully understanding Lee's conversation on computations with tangent vectors and pushforwards ... in particular I need clarification on the nature of the...
  10. Giu1iano

    Need some help with two Dimensional velocity Vectors

    Mod note: Moved from a technical section, so missing the homework template. Hi, I'm struggling to understand this problem. I would normal just wait for class but I'm away traveling for work. The question is as follows. A man has a boat that can travel at 15.0 m/s relative to the water. He...
  11. G

    MHB Proving Span of $\mathbb{R}^2$ Using Sets of Vectors

    I'm given the example that the space $\mathbb{R}^2$ is spanned by each of the following set of vectors: \left\{i, j\right\}, \left\{i, j, i+j\right\}, and \left\{0, i, -i, -j, i+j\right\}. However, it's not obvious to me how. Let $i = (s, t)$ and $j= (u, v)$ then $\left\{i, j\right\}$ means...
  12. D

    Relative Velocity of Ball on Moving Board

    Homework Statement A ball rolls with a velocity of 14 mm/s [W] on a board that is being pulled [E 60o N] at 20.0 mm/s. What is the velocity of the ball relative to the floor? b = ball x = board f = floor Homework Equations V_bf = V_bx + V_xf The Attempt at a Solution I tried to work through...
  13. Asleky

    Vector Kinematics Bonus Question

    Homework Statement A plane went 300m/s 35° south of west then 230m/s 20° east of north. What is the magnitude and direction of the 65kg pilot during the 12s turn? Homework Equations Kinematics. Vf = Vi + at, d = ViT + 0.5at^2, Vf^2 = Vi^2 + 2ad The Attempt at a Solution This was a question...
  14. S

    Tensor product of two arbitrary vectors an arbitrary tensor?

    I am trying to show that if (C^ab)(A_a)(B_b) is a scalar for arbitrary vectors A_a and B_b then C^ab is a tensor. I want to take the product of the two vectors then use the quotient rule to show that C^ab must then be a tensor. This lead to the question of whether or a not the product of two...
  15. P

    Solving Vectors Word Problem: Ground Velocity of Airplane

    Hello guys, I have a vectors word problem and I found 2 different ways to solve the same problem but I'm getting different answers. Apparently, both answers are correct since I've looked for the answer online and I found both answers from different sources, so I'm really confused now...
  16. A

    MATLAB New to Matlab, help with vectors

    So like the title says, I'm new to Matlab. I took a programming class on Fortran last year before my college changed the requirement so programming is not new to me all together. For a few of my classes we are allowed to use programs such as Matlab and Maple to help us solve problems. Most of...
  17. J

    Finding Your Way Home: Vector Components and Trigonometry

    Homework Statement Finn is lost in the woods, trying to find his way back home which he knows is 7.00 km at a 120.0° angle from his current location. He decides to travel 2.00 km at a 40.0° angle followed by another 5.00 km at a 100° angle. 1) What is his current location using a km coordinate...
  18. D

    How to find basis vectors for a+ ax^2+bx^4?

    I want to find basis for a+ax^2+bx^4 belong to p4. I am getting the following result is it right? =>a(1+x^2) + b(x^4) => basis ={1+x^2, x^4} Is that right ? Please help me any help is appreciated.
  19. B

    Can't figure out solution -- Space probe with engine thrust vectors

    Homework Statement A space probe has two engines. Each generates the same amount of force when fired, and the directions of these forces can be independently adjusted. When the engines are fired simultaneously and each applies its force in the same direction, the probe, starting from rest...
  20. M

    What is the single displacement needed for an expert golfer to make the hole?

    Homework Statement A novice golfer on the green takes three strokes to sink the ball. The successive displacements of the ball are 4.00 m to the north, 2.00 m northeast, and 1.00 m at 30.0° west of south (Fig. P3.21). Starting at the same initial point, an expert golfer could make the hole in...
  21. C

    Prove 1-norm is => 2-norm for vectors

    Homework Statement Show that ##||x||_1\geq ||x||_2## 2. Homework Equations ##||x||_1 = \sum_{i=1}^n |x_i|## ##||x||_2 = (\sum_{i=1}^n |x_i|^2)^.5## The Attempt at a Solution I am having a hard time with this, because the question just seems so trivial, that I don't even know how to prove...
  22. B

    Vectors, Hilbert Spaces, and Tensor Products

    If I ever say anything incorrect, please promptly correct me! The state of a system in classical mechanics is specified by point in phase space, the point giving us the position and velocity at a given instance. Could we rephrase it by saying a vector in phase space specifies the system? If...
  23. Phy_TR

    Help with Electric Forces Problem and Equilateral Triangles

    Homework Statement The point charges in the figure have the following values: q1=+2.1μC, q2=+6.3μC, q3=−0.89μC. Suppose that the magnitude of the net electrostatic force exerted on the point charge q2 in the figure is 0.57 N . Find the distance d and the direction (angle) of the net force...
  24. K

    I How to Write Vectors in Spherical Coordinates for Scalar Product Evaluation

    Here is the problem verbatim: The polar and azimuthal angles of a vector are Θ1 and Φ1. The polar and azimuthal angles of a second vector are Θ2 and Φ2. Show that the angle ϒ between the two vectors satisfies the relation: cos ϒ = cosΘ1*cos Θ2+sinΘ1*sinΘ2*cos(Φ1-Φ2) Hint: write out the...
  25. Dewgale

    Problem with vectors and matrices.

    Homework Statement Calculate ##(\vec a \cdot \vec \sigma)^2##, ##(\vec a \cdot \vec \sigma)^3##, and ##(\vec a \cdot \vec \sigma)^4##, where ##\vec a## is a 3D-vector and ##\vec \sigma## is a 3D-vector formed from the ##\sigma_i## vectors. Homework Equations $$\sigma_1 = \begin{bmatrix} 0 &...
  26. R

    Understanding Random Vectors and Hypersphere Distributions

    Hi There are so many different kinds of probability distributions regarding a uniform distribution of points on the surface or inside a hypersphere in 2D and 3D and it's hard to see the big picture or any pattern between them. I'm confused and exhausted :) The overall fuzzy plan is to go from...
  27. B

    Solving Subtracting Vectors Homework Problem

    Homework Statement 3 m/s [E] - 5 m/s [N] Homework Equations I don't know how to solve this- is this done algebraically or another way? The Attempt at a Solution I have no clue. Would this be different if the directions were not like this--- 3 m/s 50° east - 5m/s 67° North. I have no idea how...
  28. B

    Adding and Subtracting Vectors of Different Directions

    Homework Statement Given the initial velocity of 6m/s[North] and the final velocity of 3m/s[East], how would you find the change in velocity? Homework Equations Change in velocity= final velocity- inital velocity The Attempt at a Solution [/B] I don't know how to do this. I know that if the...
  29. M

    Covariant and contravariant basis vectors /Euclidean space

    I want ask another basic question related to this paper - http://www.tandfonline.com/doi/pdf/10.1080/16742834.2011.11446922 If I have basis vectors for a curvilinear coordinate system(Euclidean space) that are completely orthogonal to each other(basis vectors will change from point to point)...
  30. J

    Proving Vector Bisector Theorem: Simplifying Dot Products

    Homework Statement Show that vector C = (BA + AB) / (A + B) is an angle bisector of A and B. Where vectors are represented by bold font, and magnitudes are regular font. Homework Equations A ⋅ C = A C cos(θ) ⇒ cos(θ) = (A ⋅ C) / (A C) B ⋅ C = B C cos(θ) ⇒ cos(θ) = (B ⋅ C) / (B C)The...
  31. C

    Is a subset of linearly independent vectors indep?

    Homework Statement True or false. If v1... v4 are linearly independent vectors in 4D space, then {v1,v2,v3} is also linearly independent. There's a hint: Think about (c for different constant) cv1+cv2+cv3+0*v4=0 I know that linear independence means there's only the trivial solution... which...
  32. C

    Can you rearrange vectors in a set? And another misc questn.

    Suppose you have a set of vectors v1 v2 v3, etc. However large they are, suppose they span some area, which I think is typically represented by Span {v1, v2, v3} But I mean, if you're given these vectors, is there anything wrong with rearranging them? Because there's a theorem- that "an...
  33. R

    What is the largest number of mutually obtuse vectors in Rn?

    This is my question: What is the largest m such that there exist v1, ... ,vm ∈ ℝn such that for all i and j, if 1 ≤ i < j ≤ m, then ≤ vi⋅vj = 0 I found a couple of solutions online. http://mathoverflow.net/questions/31436/largest-number-of-vectors-with-pairwise-negative-dot-product...
  34. Y

    Unit Vectors as a Function of Time?

    Homework Statement Say I have a vector F something like F = c1(t) x^ + c2(t) y^ were c1 and c2 are some scalar functions of time were you plug in time to into the equation and are given some magnitude. My question seems to be can we define unit vectors/basis vector as a function of time as...
  35. PhysicsKid0123

    Time Derivative of Unit Vectors

    Quick question (a little rusty on this): Why don't unit vectors in Cartesian Coordinates not change with time? For example, suppose \mathbf{r} (t) = x(t) \mathbf{x} + y(t) \mathbf{y} + z(t) \mathbf{z} How exactly do we know that the unit vectors don't change with time? Or in other words...
  36. C

    Velocity and Acceleration Vectors

    Homework Statement Homework Equations Rotational Kinematic Equations Kinematic Equations The Attempt at a Solution I honestly have no clue how to get a vector out of this. I thought about an equation: Θ = Θ(initial) + ω(initial)*t + .5αt^2 and how maybe that v = wr could play into this...
  37. Priyadarshini

    Change in Momentum using Vectors

    Homework Statement A force F = (2ti + 3t^2j) N acts on an object moving in the xy plane. Find the magnitude of change in momentum of the object in time interval t=0 to t=2 (The bold ones are vectors) Homework Equations Ft=change in momentum The Attempt at a Solution magnitude of F = (4t^2 +...
  38. Y

    Jones Vectors and Polarization

    Homework Statement Linearly polarized light in the x direction with wave number ##k_0## travels in the z direction. It enters a medium such that a RHCP component of the wave and a LHCP component each accumulate a phase of ##n_Rk_0z## and ##n_Lk_0z## respectively, where z is the distance...
  39. S

    What does a derivative of 0 tell us about a function?

    Homework Statement So my textbook states that F = ma = m(d2r/dt2) can be integrated to give r = r0 + tv0 when F = 0. Homework EquationsThe Attempt at a Solution I've tried rewriting it as F = m(dv/dt) and integrating that to give Ft = mv + c but this is obviously not in the right form. I've...
  40. H Smith 94

    Finding the velocity of a wave

    I am currently studying a course on waves, which has a real ambiguity in the lecture notes. Essentially, I don't know how the professor got from equation \ref{eq:surf_x-y} to equations \ref{eq:vel_u} and \ref{eq:vel_w}. I have tried to work backwards to find a method but am not sure of its...
  41. CheesyPeeps

    How Do You Calculate Dot Products in Geometric Problems?

    Homework Statement Homework Equations p.q+p.r The Attempt at a Solution I've expanded p.(q+r) to give p.q+p.r. The magnitude of p is 3, and since ABE is an equilateral triangle, the magnitude of q is also 3, right? So then p.q=9, but the answer scheme states that p.q=4.5. I'm still pretty...
  42. H

    2 vectors with cylindrical polar coordinates

    Hi this isn't my homework, but it is taken from a worksheet for a Maths course(trying to refresh my rusty math), so I hope it fits in here. 1. Homework Statement two cylindrical polar vectors with same origin: P(2,55°,3); Q(4,25°,6) units in m Homework Equations a) Express in cartesian...
  43. Einj

    What Defines Future-Directed Vectors in Physics?

    Hello everyone, I have a very basic question about future-directed vectors. Are they defined as those vectors whose temporal component is positive or strictly positive? I need to check wether a certain system satisfies the null energy condition or not and I was wondering if I am allowed to take...
  44. M

    Spherical vectors and rotation of axes

    I have a velocity vector as a function of a latitude and longitude on the surface of a sphere. Let us assume I have a point V(lambda, phi) where V is the velocity. The north pole of this sphere is rotated and I have a new north pole and I have a point V'(lambda, phi) in the new system. I have...
  45. S

    Sum of null and time-like vectors

    Homework Statement Show that the sum of two future-pointing null vectors is a future-pointing time-like vector, except when the two null vectors have the same direction. Conversely, show that any time-like vector can be expressed as a sum of two null vectors. For a given time-like vector the...
  46. S

    Future-pointing and past-pointing time-like vectors

    Homework Statement I need to prove the following: a) If ##P^{a}## and ##Q^{a}## are time-like and ##P^{a}Q_{a}>0##, then either both are future-pointing or both are past-pointing. b) If ##U^{a}##, ##V^{a}## and ##W^{a}## are time-like with ##U^{a}V_{a}>0## and ##U^{a}W_{a}>0##, then...
  47. SpartaBagelz

    Inner products of vectors in the form of equations.

    I am in the process of reading through The Theoretical Minimum. One of the processes it suggests is relating to orthogonal vectors, particularly representing the right (|R>) and left (|L>) spins. Common sense says they're orthogonal but I was wondering how exactly to represent the inner product...
  48. olgerm

    Simplifying expression with vectors

    Homework Statement To simplify: ##\mid \vec b -\frac{\vec a*\vec b}{\vec a*\vec c} * \vec c \mid## ##\mid \vec b -\frac{(\vec a*\vec c)*(\vec b*\vec b)-(\vec a*\vec b)*(\vec b*\vec c)}{(\vec a*\vec b)*(\vec c*\vec c)-(\vec a*\vec c)*(\vec b*\vec c)} * \vec c \mid## Vectors may be any...
  49. P

    Is it possible to decompose a vector into non-perpendicular components?

    Homework Statement [/B]Homework Equations [/B]The Attempt at a Solution When I have to describe a motion I'm supposed to decompose a vector in two directions, for example in an inclined plane is decompose the weight in these directions: the normal to the plane and the parallel to the plane...
  50. S

    Space-like and time-like vectors

    Homework Statement Prove the following: a) If ##P^a## is time-like and ##P^{a}S_{a}=0##, then ##S^{a}## is space-like. b) If ##P^a## is null and ##P^{a}S^{a}=0##, then ##S_{a}## is space-like or ##S^{a} \propto P^{a}##. Homework Equations Using the 'mostly minus' convention, ##A^a## is...
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