Vectors Definition and 1000 Threads

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. W

    Dot product for vectors in spherical coordinates

    Hi all. I'm struggling with taking dot products between vectors in spherical coordinates. I just cannot figure out how to take the dot product between two arbitrary spherical-coordinate vectors ##\bf{v_1}## centered in ##(r_1,\theta_1,\phi_1)## and ##\bf{v_2}## centered in...
  2. PhotonSSBM

    Perpendicular Unit Vectors in the x-y Plane: Is My Solution Correct?

    Homework Statement From Kleppner and Kolenkow Chapter 1 (Just checking to see if I'm right) Given vector A=<3, 4, -4> a) Find a unit vector B that lies in the x-y plane and is perpendicular to A. b) Find a unit vector C that is perpendicular to both A and B. c)Show that A is perpendicular to...
  3. H

    Calculating Vectors and Components: Finding A*B and AxB Components

    Homework Statement Vector A lies in the yz plane 65.0° from the positive direction of the y axis, has a positive z component, and has magnitude 5.10 m. Vector B lies in the xz plane 42.0° from the positive direction of the x axis, has a positive z component, and has magnitude 1.70 m. Find (a)...
  4. kq6up

    Coefficients of a Superposition of State Vectors?

    Homework Statement (f) At t = 0, a particle of mass m trapped in an infinite square well of width L is in a superposition of the first excited state and the fifth excited state, ψs(x, 0) = A (3φ1(x) − 2iφ5(x)) , where the φn(x) are correctly-normalized energy eigenstates with energies En. Which...
  5. G

    How to find reciprocal lattice vectors

    So I know that the basis vectors of an FCC in a symmetric form are: a = \frac{a}{2}(\hat{x} + \hat{y}) b = \frac{a}{2}(\hat{y} + \hat{z}) c = \frac{a}{2}(\hat{x} + \hat{z}) And that the reciprocal lattice vectors are the basis vectors of the BCC cells. I'm having a hard time doing the...
  6. eliw00d

    Biot and Savart Integral using Vectors

    How would I go about setting up a Biot and Savart Integral using Vectors? Here is an exercise we had in class: I tried to set it up using Vectors, and figured dl to be <-L,L> and r to be <½L, -½L>. After the cross product, I am not sure how to handle the integration, since r can vary. Would...
  7. K

    Add 3 Vectors: Mag & Dir Calculations

    Homework Statement Three vectors, A, B and C each have a magnitude of 50 units. Their directions relative to the positive direction of the x-axis are 20°, 160° and 270°, respectively. Calculate the magnitude and direction of each of the following vectors. a)[/B]→A+ →B+ →C b)→A− →B+ →C c)2 (...
  8. P

    Why Does Mass M Move at u/cosθ in a Pulley System?

    Homework Statement In the arrangement as shown in the figure below, the ends P and Q of an inextensible string move downwards with uniform speed u. Pulleys A and B are fixed. Mass M moves upward with a speed: a. 2ucosθ b. u/cosθ c. 2u/cosθ d. ucosθ Homework Equations None, I am not sure...
  9. T

    Expanding a function in terms of a vector

    Homework Statement ## L (v^2 + 2 \pmb{v} \cdot \pmb{ \epsilon } ~ + \pmb{ \epsilon} ^2)##, where ## \pmb{\epsilon}## is infinitesimal and ##\pmb{v}## is a constant vector (## v^2 ## here means ## \pmb{v} \cdot \pmb{v} ## ), must be expanded in terms of powers of ## \pmb{\epsilon} ## to give...
  10. S

    Calculating Displacement: Understanding Vectors in Physics

    A car travels 10 km due EAST then 12. Km NW what is Magnitude of the car's displacement. The answer that I got in my book is 8.8 Could anyone-please-explain ?The Attempt at a Solution 6.6 km[/B]
  11. C

    Resultant of 3 vectors along the sides of an equilateral triangle

    Homework Statement Hi all, It is a homework problem, but I really don't quite understand the question. It reads- "3 forces of magnitudes 10N, 20N, and 30N acting on a point are parallel to the sides of an equilateral triangle, taken in order. Find their resultant"Homework EquationsThe Attempt...
  12. Sarah00

    Projectile Motion & Vectors: Acceleration and Axis Conventions Explained

    Homework Statement Homework Equations - The Attempt at a Solution I know that the acceleration is downward always with value of 10m/s2 The answer is D? because j denote vertical axis and negative sign means downward? [/B]
  13. S

    Difference between Co-variant and Contra-variant vectors?

    I understand that Contravariant vectors have an upper index and co-variant vectors use a lower index. But why is one preferred over another in a specific physical situation? I am just struggling with which form is preferred, and why one would bother trying to raise or lower the index in a...
  14. J-dizzal

    Work and force problem with vectors

    Homework Statement A machine carries a 4.0 kg package from an initial position of di=0.6m##\hat i## + 0.7m##\hat j## + 0.26m##\hat k## at t = 0 to a final position of df= 11.5m##\hat i## + 14.0m##\hat j## + 10.2m##\hat k## at t = 15.0 s. The constant force applied by the machine on the package...
  15. A

    Rotation of Vectors: Comparing Matrices

    < Mentor Note -- thread moved to HH from the technical math forums, so no HH Template is shown > Hello, I have a problem with rotation matrices, its just a comparison problem. Θ must be 240 or -120, I don't know how the book show the answer like that, these are the two matrices...
  16. E

    Solving Vectors & Surfing Problem at Waikiki

    Hello, Here's the problem: Suppose we orient the x-axis of a two-dimensional coordinate system along the beach at Waikiki. Waves approaching the beach have a velocity relative to thTe shore given by v = (1.3 m/s)y. Surfers move more rapidly than the waves, but at an angle to the beach. The...
  17. blue_leaf77

    Linear dependence of two vectors

    Suppose the vectors ##v_a## and ##v_b## are linearly independent, another vector ##v_c## is linearly dependent to both ##v_a## and ##v_b##. Now if I form a new vector ##v_d##, where ##v_d = v_b+cv_c## with ##c## a constant, will ##v_d## be linearly independent to ##v_a##? I need to check how I...
  18. Cosmophile

    Concerning Vectors in Scalar Form

    Hey, all. I have a question concerning the treatment and use of vectors when solving problems (or in general, really). I know that vectors have both magnitude and direction, while scalars only have magnitude. However, in solving problems and looking at how others have solved them, I've noticed...
  19. vktsn0303

    Understanding Tangent Vectors at Points on a Curve

    I was reading about the tangent vector at a point on a curve. It is formulated as r' = Lim Δt→0 [r(t+Δt) - r(t)] / Δt (sorry for the misrepresentation of the 'Lim Δt→0 ') where r(t) is a position vector to the curve and t is a parameter and r' is the derivative of r(t). All I can...
  20. Alpha123

    What is the velocity of particle x with reference to Y?

    Homework Statement Particle X moves with a velocity of 15 m/s[R]. Particle Y moves with a velocity of 5.0 m/s[L]. What is the velocity of particle X with reference to particle Y? The correct answer is 20 m/s (R). I do not understand what velocity in reference to particle Y means, and how to...
  21. RyanH42

    What are the ##\vec{u}_r## and ##\vec{u}_θ## vectors?

    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > In textbook I am troubling understanding the question.Actually I don't know the terms ##\vec{u}_r## and ##\vec{u}_θ## Here the question. A particle moves according to the polar equation...
  22. C

    Classical Good books on Vectors for Newtonian mechanics?

    Hi, I'm internested in a good book that teaches vectors (and perhaps tensors?) so i can better understand books on classical/Newtoniam mechanics. I know the basics of vectors, but i still get confused when i se them in physics books and don't completely understand what's going on when physics...
  23. RyanH42

    Basis and Components (Vectors)

    Homework Statement Let ##u_1,u_2,u_3## be a basis and let ##v_1=-u_1+u_2-u_3## , ## v_2=u_1+2u_2-u_3## , ##v_3=2u_1+u_3## show that ##v_1,v_2,v_3## is a basis and find the components of ##a=2u_1-u_3## in terms of ##v_1,v_2,v_3## Homework Equations For basis vecor...
  24. M

    How Do You Find a Vector with a Specific Magnitude in the Opposite Direction?

    Homework Statement Find a vector in the direction opposite to <-4,1,2>, that has a magnitude of 3. Homework Equations I think that I did the first part of the problem correctly: <-4,1,2> magnitude= sqrt[ (-4)^2+1^2+2^2 ] = sqrt(16+1+4) = sqrt(21)...
  25. R

    Unit Vectors for Polarization and Wave Vector Directions

    Homework Statement I am having difficulty understanding the very first step of the following solved problem (I understand the rest of the solution). How did they obtain the expressions for ##\hat{n}## (the direction of polarization), and ##\hat{k}## (the unit vector pointing in the direction...
  26. Nile Anderson

    Mathematical Modelling, Vectors and Parametric Equations

    Homework Statement Sorry to disappoint the math fanatics but no this is not a question that integrates all three topics at once but individual ones. I still need assistance though with the following more so in the reasoning behind them as I feel my logic is flawed...
  27. O

    Cross product of 2 vectors of same magnitude

    Homework Statement Vectors A and B both have magnitude M. Joined at the tails, they create a 30' angle. What is A x B in terms of M? Homework EquationsThe Attempt at a Solution 0? OR M^2? Sqrt(3)M/3?
  28. kapoor_kapoor

    About vectors and vector products

    If two physical quantities are being multiplied , is there any way to know that the result will be a scalar of vector.. Moreover if two vectors are being multiplied how can we know that we have to apply cross or dot product??
  29. N

    How Does Tangential Velocity Relate to Vector Products in Rotational Motion?

    The tangential velocity of a body rotating about the centre point "O" is given by v=w.r, where w is angular velocity and r = radius. give that the vectors w = 3i - 2j + 7k r = 2i + 5j - 3k a) Calculate the magnitude of velocity b) the vector product in the form i+j+k So far I have the vector...
  30. M

    Find closest possible points between lines? (vectors)? Edit

    Homework Statement [/B] Find points P,Q which are closest possible with P lying on the line x=8+1t y=8+1t z=7−3t and Q lying on the line x=231−6t y=−10−17t z=71−13t 3. Attempt at solution Hi, I am at loss as to how to do this. I know that from the equations I can get point (8,8,7) and...
  31. S

    Figuring out Bravais lattice from primitive basis vectors

    Homework Statement Given that the primitive basis vectors of a lattice are ##\mathbf{a} = \frac{a}{2}(\mathbf{i}+\mathbf{j})##, ##\mathbf{b} = \frac{a}{2}(\mathbf{j}+\mathbf{k})##, ##\mathbf{c} = \frac{a}{2}(\mathbf{k}+\mathbf{i})##, where ##\mathbf{i}##, ##\mathbf{j}##, and ##\mathbf{k}## are...
  32. C

    Find Unit Vectors for f(x,y) w/ D_uf=0

    Homework Statement For f(x,y)=x^2-xy+y^2 and the vector u=i+j. ii)Find two unit vectors such D_vf=0 Homework Equations N/A. The Attempt at a Solution Not sure if relevant but the previous questions were asking for the unit vector u - which I got \hat{u}=\frac{1}{\sqrt{2}}(i+j) for the maximum...
  33. B

    Why Do Engineers Use Pullbacks and Pushforwards in Mathematics?

    Hello I am a mechanical engineer who is teaching himself the math of exterior algebra and differential forms. It is not easy for me and I have had many SIMPLE stumbling blocks due to my not respecting algebra. May I ask for help on some simple aspects? (Please be patient with me.) My...
  34. J

    Killing vectors and momentum conservation

    Consider the flat FRW metric in Cartesian spatial co-moving co-ordinates: ##ds^2=-dt^2+a(t)^2(dx^2+dy^2+dz^2)## As I understand it, since the metric does not depend on the the spatial co-ordinates, there exist Killing vectors in the ##x##,##y##,##z## directions. Does this imply that the...
  35. D

    How to compute the surface height based on normal vectors

    Suppose I have already found the surface normal vectors to a set of points (x,y), how do I compute the surface height z(x,y)? Basically what I have are the normal vectors at each point (x,y) on a square grid. Then I calculate the vectors u = (x+1,y,z(x+1,y)) - (x,y,z(x,y)) and v =...
  36. B

    MHB Vectors and their derivative proof

    The question suggests that r(t) = (x(t),y(t),z(t)) is a position vector along some curve where t goes from negative to positive infinity. Now suppose t has been chosen so that 1 = the dot product of dr/dt and dr/dt. Show that 0 = the dot product of dr/dt and d^2r/dt^2. I have attempted to...
  37. S

    Why is it advantageous to use vectors D and A in problems?

    At the moment we are working through problems in Griffiths' Electrodynamics textbook and it got me thinking... In magnetostatics we have the magnetic vector potential A and in the use of dielectrics problems we have the vector D. Why is it advantageous to use these vectors and not just stick to...
  38. leafjerky

    Deriving formulas used for vectors in physics.

    Hey guys and gals, I'm taking an online physics course just to kind of learn the basics before I take the real thing this summer. The course is from OpenYale for those interested (oyc.yale.edu). Anyways, the professor was talking about some formulas for finding ##\vec{r}(t) = r(i(cos\omega t) +...
  39. F

    Calculate Fb Reaction at Point A for 30° Triangle

    hello The below structure (the triangle) is connected to fixed point A that is a hinge (can rotate freely). Fc force is perpendicular to (ac) and Fb is horizontal. If the (bac) angle is 30 degrees, calculate the reaction at A. My attempt: Since Fc is perpendicular to (ac) it doesn't apply any...
  40. D

    Kinematics: given 2 position vectors, time, and V of earlier

    If you know the position vectors of a particle at two points along its path, change in time between the two positions, and the particle's velocity at the earlier point, what quantities can you calculate? a)average acceleration b)final velocity c)average velocity d)displacement My answer was...
  41. R

    Calculating x From Collinear Vectors c and d

    Homework Statement If the vectors a and b are non-collinear and the vectors c = (x-2)a + b and d = ( 2x + 1)a - b , are collinear then x is equal to Homework Equations c x d = |c| |d| sin θ n where n is unit vector The Attempt at a Solution Since c and d are collinear there cross product...
  42. J

    Complex Vectors vs Normal Vectors

    The way I understand it, they both have rectangular forms which are easy for addition/subtraction. Now I realize that the polar form of a complex vector can be simplified into an exponential, which is ideal for multiplication/division. But this is what confuses me; vectors don't multiply/divide...
  43. Safinaz

    Polarization vectors of spin-1 particles

    Hi there, In the decay of ## B \to D^* l \nu ##, I found that the polarization vectors are described as following: In the B rest frame the helicity basis ## \bar{\epsilon}(0)= \frac{1}{\sqrt{q^2}} (p_{D^*},0,0,-q_0), \\ \bar{\epsilon}(\pm)=\pm \frac{1}{\sqrt{2}} (0,\pm 1,- i,0), \\...
  44. nuuskur

    System of vectors, linear dependence

    Homework Statement Prove that if in a system of vectors: S_a =\{a_1, a_2, ..., a_n\} every vector a_i is a linear combination of a system of vectors: S_b = \{b_1, b_2, ..., b_m\}, then \mathrm{span}(S_a)\subseteq \mathrm{span}(S_b) Homework EquationsThe Attempt at a Solution We know due to...
  45. B

    Calculating Normal Vectors for Particle Motion

    Homework Statement [/B] This problem is from Jon Rogawski's Calculus-Early Transcendentals At a certain moment, a moving particle has velocity v={2,2,-1} and a={0,4,3}. Find T, N and the decomposition of a into tangential and normal components.Homework Equations ANYTHING IN [ ] REPRESENTS A...
  46. binbagsss

    Product of Tangent Vectors & Affine Parameter

    If ##\sigma## is an affine paramter, then the only freedom of choice we have to specify another affine parameter is ##a\sigma+b##, a,b constants. [1] For the tangent vector, ##\xi^{a}=dx^{a}/du##, along some curve parameterized by ##u## My book says that ' if ##\xi^{a}\xi_{a}\neq 0##, then by...
  47. S

    What are the forces acting on a sliding box?

    I was asked to draw a free body diagram to derive the equation tan θ = µs for the following situation: A box sliding down an inclined plane. My FBD has 3 forces - gravitational forces pointing downward (horizontally) <-- longest vector - normal force perpendicular to the box - frictional...
  48. H Smith 94

    Visualising the Conjugate Transposition of a Vector

    Hi there! As you might have already guessed, I'm referring primarily to the 'geometrical' difference (is there such geometry in Hilbert space?) between ##n##-dimensional state vectors | \psi \rangle = \left( \begin{matrix} \psi_1 \\ \psi_2 \\ \vdots \\ \psi_n \end{matrix} \right) and their...
  49. D

    Transforming Vectors from Basis B to C: A Confusing Matter

    Suppose a change of basis from basis ##B## to basis ##C## is represented by the matrix ##S##. That is, ##S## is the transformation matrix from ##B## to ##C##. Now if ##t## is a given linear transformation, ##t:~V\rightarrow V##, with eigenvectors ##\epsilon_i##, say, and ##T## is the...
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