The meaning of Reference point What is Position? What is Location and where walk it differ from Position? just how to express the position in a system of coordinates? Kinematics learning MaterialTutorial IDTitleTutorialVideoTutorialRevisionNotesRevisionQuestions
3.2Position, recommendation Point


In the previous Tutorial, "Types of Motion", we described the activity as "the phenomenon in which an item changes its ar over time." But, is it constantly easy to know whether an object is relocating or not?

Consider the adhering to examples:

You room looking in ~ the downloading and install bar ~ above a PC screen when a an extremely heavy record is being downloaded and also the web is very slow. You are observing the stars throughout the night in a clean sky. You space looking the minute hand the a wall clock.

Is it basic to detect any motion in the above examples? Why?

Which activity would assist you find whether the abovementioned objects are moving or not? Why?

The an interpretation of recommendation point

Let"s try to explain the concept of reference suggest by offering answers come the questions posed in the "Introduction" section.

You are watching: What is a reference point in physics

1. The downloading and install bar appears unmoveable. At very first sight, it appears the downloading procedure has stopped. Friend can inspect this by putting the cursor in ~ the end of the orange bar, which mirrors the downloading and install progress. ~ a while, friend can inspect whether the orange bar has moved ~ above the right of the cursor or not. If yes, the downloading procedure is active. Therefore, the cursor acts as a reference allude for you together it helps knowledge whether the downloading and install progress bar is relocating or not.

Look at the figure below:


2. The shining star is contempt on the left of pyramid in the an initial figure. After ~ a while, the "shifts" on the right of the pyramid. In this way, the pyramid acts as a reference point, i beg your pardon helps us to recognize whether the stars room in the same ar as prior to or they "have moved".

Look at the figure:


3. In the figure below, the star in the wall helps us understand that the clock is working properly as the minute hand has moved in respect come the star. Therefore, the (the star) acts together a reference point.


In all the above examples, that was clearly outlined the necessity and also importance of a reference suggest from which we start making any kind of measurement or estimate in order to detect any change in object"s location.

Thus, by definition, "A fixed suggest with respect to which a body changes its place is called Reference suggest or Origin."

When dealing with calculations in Kinematics, reference suggest is generally the beginning of the name: coordinates system, no matter whether the device is 1, 2 or 3 dimensional. Reference allude (origin) is commonly denoted through the number 0 or the letter O.

What is Position? how does it different from Location?

We can present the location of things by a finger, or by illustration a little dot in the location where the thing lies. If the object is voluminous, we usually placed a small dot at the object"s center to show its place as in the figure below.


It is evident that location does not suggest the use of any kind of reference point or coordinate. Therefore, no numerical worths are affiliated when taking care of the location of an object.

On the various other hand, Position is a physical quantity that shows exactly how far an object from the origin (reference point) is. Place not only has actually a size (numerical value) however it additionally has a direction. It is no the same thing if we say, "the object is 6m ~ above the left the the referral point" and also "the thing is 6m on the best of the reference point" although the distance from the origin (reference point) is the exact same in both situations (6 m).


Thus, there are two guys in the figure; every of them is at 6m from the tree, which in this instance acts together a reference point or origin. Therefore, that is obvious it is not enough knowing only the distance from the reference point but us must recognize the direction as well. Only then, us can specifically determine the position of a given object.

As we discussed in tutorial 2.1 "Vectors and Scalars in", a amount for i m sorry direction info is compelled is known as "vector quantity." This is the instance for the position of one object.

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By definition, "Position is a vector amount that shows exactly how far an object is native the beginning in a provided direction."

Position can be positive, an adverse or zero. It have the right to be positive when the location of the object is at the positive component of the position axis. Because that example, the place of the eco-friendly bicycle shown listed below is optimistic as its ar is at (+4) m. Together for the position of the blue bicycle, that is an adverse because its location is in ~ (-1) m. (Remember, for voluminous and irregularly shame objects we think about the actual location at the center of the object). Position deserve to be zero when the thing is situated at the reference point.


Position in the mechanism of coordinates

It is well-known that in a device of collaborates we deserve to assign a letter to every direction available. Thus, if over there is only one direction easily accessible (1-D) as displayed in the over figure, we signify the axis by the letter x and also the object"s place by the vector x⃗ or Ox)⃗. We deserve to write