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Position Vector Explained: Formula, Uses & Examples

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How to Calculate and Interpret the Position Vector in Physics

The Position Vector which is said to be a straight line having one end fixed to a body and the second end that is attached to a moving point. And this is used to describe the position of the point relative to the body. As the point moves the vector’s position will change in length or in direction or at times in both direction and length. If  drawn to some scale, then the change which is in length will signify a change which is in the magnitude of the vector. That is while a change which is in direction will signify a vector that is rotating.

 

In this article we are going to discover what a vector is as well as a few other important points.


Displacement of Vectors

The velocity and the Position Vectors which are of a particle are illustrated in Figure given below. The Position Vector which is denoted by r extends from the origin to the particle. While the velocity vector which is denoted by letter v points in the direction of the particle’s motion. The other variables which are appropriate are for describing a moving particle that can be defined in terms of these variables and the elementary variables as well.

 

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The momentum which is denoted by letter p of the particle is equal to the product of the velocity and mass that is v of the particle

p=mv.

 

We shall find the momentum which is useful for describing the motion of electrons in a system which is extended such as a crystal.

 

The particle's motion which is moving about a center of force can be described using angular momentum . That is defined to be the cross product of the position and vectors momentum which is given as:

ℓ=r×p.

 

The cross product that is of two vectors is a vector which is having a magnitude equal to the product of the magnitudes of the two vectors and at times the same as the sine of the angle between them. This is denoting the angle which is between the momentum and Position Vectors by θ as the magnitude of the momentum that is the angular vector momentum can be written as:

|ℓ|=|r||p|sinθ.

 

Vector of Physics

We can use a vector which is known as the Position Vector to tell us the location of one object that is relative to another. Specifically we can say that a Position Vector is:

 

A vector that indicates the position of a given point with respect to an arbitrary reference point example origin.

 

In this article we will discuss the following aspects of Position Vectors:

  • Explain what is a Position Vector?

  • And how to Find the Position Vector?

 

Often, we have noticed that the vectors that start at the origin and terminate at any arbitrary point are known as Position Vectors. These are said to determine the position of a point with reference to the origin of that point.

 

The direction of the vectors or the Position Vector generally points from the origin towards the given point. In the coordinate system of c\Cartesian if point O is the origin and Q is some point that is x1, y1, then the directed Position Vector from point O to point Q is represented as OQ. In the space which is three-dimensional if O = (0,0,0) and Q = (x1, y1, z1), then the Position Vector denoted by r of point Q is represented is:

r = x1i + y1j + z1k

 

Now let’s suppose that we have two vectors, that are A and B, with Position Vectors we write a = (2,4) and b = (3, 5) respectively. We can then write the coordinates of both the vectors that are A and B as:

A = (2,4), B = (3, 5)

 

Here before determining the Position Vector of a point we first need to determine the coordinates of those particular pointst. Let’s suppose that we have two points, namely M and N. where  the point M = (x1, y1) and N = (x2, y2). Next we want to find here the Position Vector that too from point M to point N the vector MN. To determine this Position Vector, we simply subtract the corresponding components of M from N:

Written as : MN = (x2-x1, y2-y1)

 

Formula

If we consider a point denoted by letter P. Which has the coordinates that are xk, yk in the xy-plane and another point written as Q. Which has the coordinates denoted by xk+1, yk+1. The formula which is to determine the Position Vector that is from P to Q is written as:

PQ = ((xk+1)-xk, (yk+1)-yk)

 

We can now remember the Position Vector that is PQ which generally refers to a vector that starts at the point P and ends at the point Q. Similarly if we want to find the Position Vector that is from the point Q to the point P then we can write:

QP = (xk – (xk+1), yk – (yk+1))


Definition of Position Vector:

Position Vector - Explanation, Formula, and FAQs Position Vectors (also Positioning Vector) are a mathematical representation of the position of an object in space. They can be used to calculate relative distances between objects, as well as directions and angles without having to draw them out. Position Vectors are commonly used in engineering and physics calculations, but they can also be useful for everyday math problems such as measuring the distance from one point on a map to another. We will explain what Position Vectors are and how you can use them by answering some common questions that people have about this topic.


The Position Vector is used to find the distance and direction from point-A to point B. Position Vectors are commonly used in engineering and physics calculations, but they can also be useful for everyday math problems such as measuring the distance from one point on a map to another.


How to Position Vectors helps us to find the length of each vector. Position Vectors are commonly used in engineering and physics calculations, but they can also be useful for everyday math problems such as measuring the distance from one point on a map to another.


What is the Formula for Calculating Position Vector:

If we consider point A with coordinates (x, y) and point B with coordinates (X, y'), the Position Vector from A to B is simply given by:

Position Vector = X - x y' - y


What's the Difference between Magnitude and Direction?

The magnitude of a vector is simply its "size" or "length", while the direction indicates which way it points. For instance, if you have a vector with a magnitude of three and a direction of 45 degrees, it would be three units long measured along the angle specified by 45 degrees. If you rotated that vector so that it pointed in the opposite direction, its length would still be three units, but its


FAQs on Position Vector Explained: Formula, Uses & Examples

1. What is a position vector in Physics?

A position vector, denoted as &vec;r, is a vector that represents the location of a point in space relative to a fixed reference point, usually the origin (0,0,0) of a coordinate system. Its tail is fixed at the origin, and its head points directly to the specific point. It uniquely defines a point's location by specifying both its distance and direction from the origin.

2. What is the formula for a position vector in 3D space?

For a point P with coordinates (x, y, z), the position vector &vec;r is given by the formula:
&vec;r = xî + yĵ + z&kcirc;
Here, î, ĵ, and &kcirc; are the unit vectors along the X, Y, and Z axes, respectively. The coefficients x, y, and z represent the scalar components of the vector along each axis.

3. How do you write the position vector for a point with coordinates (2, -4, 5)?

To write the position vector for the point (2, -4, 5), you use the standard formula by assigning the coordinates to their respective unit vectors. The position vector &vec;r would be:
&vec;r = 2î + (-4)ĵ + 5&kcirc;
This simplifies to &vec;r = 2î - 4ĵ + 5&kcirc;.

4. What is the main difference between a position vector and a displacement vector?

The key difference lies in what they describe:

  • A position vector specifies the absolute location of a single point with respect to the origin.
  • A displacement vector represents the change in position between two points. It is a straight line drawn from an initial position to a final position and is independent of the origin. It is calculated by subtracting the initial position vector from the final position vector (Δ&vec;r = &vec;r₂ - &vec;r₁).

5. What are some important real-world uses of position vectors?

Position vectors are fundamental in many fields. Key applications include:

  • GPS and Navigation: Your location on a map is determined by a position vector relative to a reference point, like the Earth's centre.
  • Physics and Engineering: Used to describe the location of objects and calculate forces, electric fields, and gravitational fields.
  • Robotics: A robot's arm uses position vectors to know the exact location of its gripper relative to its base.
  • Astronomy: To map the locations of stars, planets, and other celestial bodies in space.

6. Why is the origin considered a crucial reference for any position vector?

The origin serves as a fixed, universally agreed-upon reference. Without a common origin, the term "position" becomes ambiguous. The origin provides a zero point from which all distances and directions are measured consistently. This ensures that the position vector for any given point is unique and allows for meaningful comparison and calculation between different vectors within the same coordinate system.

7. Can a position vector have a negative component, and what does it signify?

Yes, a position vector can have negative components. A negative component, like -yĵ, simply signifies that the point's location is along the negative direction of that particular axis. For example, the position vector &vec;r = 3î - 2ĵ points to a location that is 3 units along the positive X-axis and 2 units along the negative Y-axis from the origin.

8. How does a position vector relate to the concepts of velocity and acceleration?

Position, velocity, and acceleration are intrinsically linked through calculus. If a particle is moving, its position vector &vec;r(t) changes with time.

  • The instantaneous velocity (&vec;v) is the rate of change of the position vector: &vec;v = d&vec;r/dt.
  • The instantaneous acceleration (&vec;a) is the rate of change of the velocity vector: &vec;a = d&vec;v/dt = d²&vec;r/dt².
Thus, the position vector is the foundational quantity in kinematics from which motion is described.

9. What is the conceptual difference between a position vector and a unit vector?

The core difference is their purpose:

  • A position vector describes location. It has a magnitude (distance from origin) and a direction. Its magnitude is typically not equal to one.
  • A unit vector describes direction only. It is defined as having a magnitude of exactly 1. Its sole purpose is to point in a specific direction.
You can find the unit vector in the direction of a position vector &vec;r by dividing the vector by its own magnitude: &rcirc; = &vec;r / |&vec;r|.

<h1>Position Vectors in Physics: Definition, Formula, and Applications</h1> <strong>Summary:</strong> Position vectors are straight lines with one end fixed to a body and the other attached to a moving point, describing the point's position relative to the body. They change in length, direction, or both as the point moves. Position vectors extend from origin to particle, with velocity vectors pointing in motion direction. Key relationships include momentum p=mv and angular momentum ℓ=r×p. In Cartesian coordinates, a position vector from origin O to point Q(x₁,y₁,z₁) is r = x₁i + y₁j + z₁k. For position vector from point M(x₁,y₁) to N(x₂,y₂), the formula is MN = (x₂-x₁, y₂-y₁). Position vectors determine relative distances, directions, and angles between objects, commonly used in engineering and physics calculations for measuring distances and analyzing motion. <strong>Questions/Concepts Covered:</strong> <ul> <li>What is a position vector and how does it describe particle motion and displacement?</li> <li>How to calculate position vectors using coordinate geometry formulas?</li> <li>What are the applications of position vectors in momentum and angular momentum calculations?</li> </ul> <strong>Keywords:</strong> <ul> <li>Position vector definition physics</li> <li>Cartesian coordinate system vectors</li> <li>Angular momentum cross product</li> <li>Vector displacement formula</li> <li>Particle motion description</li> </ul>