# Uniform Circular Motion – Circular Motion – Physics Class 12

Do Subscribe To Ekeeda Channal and press bell icon to get updates about latest Engineering HSC and IIT-JEE Mains and Advanced videos. Hello students in this video we’ll discuss about Uniforms of Circular Montion type in your frequency of the body performing simple harmonic motion or any sort of circular motion so we’ll discuss that that is UCM Uniforms Circular Motion. Hello students let us start with uniform circular motion so it is 1.4 uniform. circular motion insult we do say it is UCM We know that the circle motion is that the radius vector magnitude remains constant if we have a motion like this a particle in a circular path from here to here any position this is the center the particle can be at any position this is the radius vector suppose this is a point one and two this is a vector position vector R 2 vector we know that the directions are different about the magnitudes are same so if we have a condition like magnitude of a radius vector or position vector is constant this implies circular motion the magnitude of radius vector is constant then it is sort of motion then what is uniform so promotion how this what uniformity is as to circular motion the uniformity is attached with the one condition that we impose on the body which is moving and that condition is that you keep the speed constant so if the speed that is the magnitude of the instantaneous velocity remains constant we call this as linear speed if the linear speed of the particle is constant then we say it is performing uniform circular motion so if we have these two conditions together that will make uniform circular motion that means the definition is that if a particle moves along the circumference of the circle such that it’s a linear speed remains constant then the motion is uniform circular motion okay if this is the definition this is the definition of UCM if the particle if the linear speed of the particle moving if the linear speed of the particle moving in a circular path is constant the motion is said to be you cm so let me discuss a few more things that if I have a situation like this and suppose that the particle is moving in the anti clockwise sense then the velocity vector get the drawn by doing a tangent at any point suppose the particle is here I have to draw a tangent like this this is the direction of velocity vector because the magnitude is constant so here also it is tangent here also it is transient here also distended so this is the direction of velocity vector we must keep in mind that the direction of the velocity vector is changing in reasons or each and every instant of time qu as it goes along the curve of the circumference that is circular motion and the magnitude if I keep Austin the speed remains the same that is U shape so we have to say that the velocity is not constant so it is wrong if you write that the linear velocity is constant velocity is never constant because the direction is changing any vector to the constants is the direction and magnitude both tend to be same in this situation it is only the magnitude which is kept constant therefore it is UCM so what are the things that you can write about UCM just what are the quantities which are constant in UCM just let me tell you I I do not write that when linear speed is constant angular velocity is constant angular speed is constant angular acceleration is zero because the Omega is constant there is no alpha to make Omega change the kinetic energy is constant because panting Energy’s 1/2 MV squared is the speed square not it is the velocity speed square speed is constant that means is constant angular momentum is constant in a circular path the angular momentum will remain constant so accelerations what about linear acceleration linear acceleration is not constant because the direction is changing that will study up towards what is the acceleration that acceleration is called centripetal acceleration that releases afterwards now the velocity is not constant and these are the things next we will move to the definitions of and what are the examples of you see mu let us take few examples then we’ll define what is time period in frequency of body in a circular motion now let us take the example of you chien you see M we will take some example example of you see M is the body moving in a circular path like hands of watch whether it is minivan 2nd and orange it is moving at constant speed discovering the angle and many more examples you can have on you see and the motion of planets around the Sun though it is exactly not constant speed because when when you think of part of the planet around Sun as circular then it is constant that is UCM but Kepler says that the path is elliptical so it is not possible when it approaches the Sun it speed keeps on increasing and when it take moves away from the Sun then speed starts decreasing but in any way you can say that the planet motion around the Sun is uniform so promotion as long as the path is considered to be as uniform so promotion you can have electrons moving around the nucleus that also is uniform so promotion the speed is constant in case of electron in the hydrogen atom of first orbit the speed is nearly 2 times 10 to the power 6 meter per second so that is also constant so electrons around nucleus electrons around decrease that is also constant and the áfourá electron in hydrogen art of it is 2 10 to the power 6 meter per second this is the speed in the first orbit of hydrogen atom H item the first orbit the speed of electron is this one first of it n is 1 so these are examples we can have many more such examples now will define what is a time period and frequency of subtle motion time to here suppose the particle is moving in a circle suppose the particle is moving in a circle now suppose that particle is moving in a circle is the particle P and so this is a particle P and it is moving in anti-clockwise sense now how it’s time to take complete one revolution starting from this point it comes back to the same point again when it completes one rotation how much time it will take that is known as time period so tightly so type in it is the time just complete one rotations it may be an apron around the nucleus or the planet around the Sun for example earth takes 365 days to complete one rotation though it is not exactly 365 days some more hours is there similarly the spinning of Earth on its own axis spinning of earth amongst all X’s it takes to differ arts to complete one rotation that is also type it is 24 arts so this is how it is defined time period the unit is always in seconds frequency is what what is frequency let us write that right there I use the symbol capital D frequency I use the symbol small n it is the number of revolutions or patience completed in a given second in any time it is the of but the Aleutians but if the number of revolutions completed in one second in once again how much sets up the revolutions is making suppose in one second it repeats two relations then it’s frequencies – if it is half of the total path of your path then it is sequence is half so in one second how much is the portion it is covering that is frequency and the unit of frequency is much it is the revolutions per second how much revolutions is completing revolutions but second so this is written as r PS revolutions per second this is an SI system and if it is in R P and revolutions per minute then you to convert to our peers in numerical C will have to convert this into RPS suppose example we have 60 rpm this implies 60 revolutions per minute that means in 1 minute that is in 60 seconds of these 60 revolutions so you once again how much revolutions one want revolutions per second so to convert that whatever is the value here divided by 60 that becomes RPS so it is one other piece so when I suppose it is a 180 rpm this implies 180 divided by 60 so it is 3 R PS that means once again 3 Louvre Aleutians in 60 seconds it is 180 revolutions that is in 1 minute it is 1 it revolutions so if this apply you will be basically dealing with rpm and RPS you don’t have to do any about the heart factor that is very used in waves now this is about time period and the frequency and I must know how their letter just I’ll give you what now formula a time period is reciprocal of frequency similarly the other way you can say that the frequency is reciprocal of time freedom of the volution okay so these are the things and take note of this so this is all about in this video and the next video we’ll discuss something else thank you

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