Today our topic is rest and motion very interesting and conceptual here we will not read physics, we will learn physics for better understanding please go through every post topic lets start.
An Object is at certain position and after some time we observe object changes its position then we say object is under motion means change of position is motion there may be some reason suppose we are applying forces from all the side to object and object does not change its position then we say object is at rest.
Rest and motion concept for bodies
When a force is applied upon a body then body start to move then it is also said to be object is under motion so we have to study so many things we a body moves all this knowledge of motion study in physics a branch of physics called Mechanics then what is mechanics ? knowledge of motion now this mechanics is divided in three parts.
1 Statics there may be some reason that particle is not moving its speed and its motion is zero wait zero speed is a speed there may be certain reason why body is not moving and we study about this reason is called statics hence study of conditions when a body is not moving called statics.
2 Kinematics this is branch of knowledge we study about motion and its relation between different quantities like velocity, distance, displacement, acceleration, speed, initial velocity, final velocity, all this things we study in kinematics except the cause of motion, we don’t study here the cause of motion means who is responsible for this motion we don’t study here we only study here different quantities like velocity, distance, time, acceleration relationship when body is under motion how they are related to each other in different state of motion like straight line motion, plane motion (Projectile motion ) space motion, circular motion whatever be the motion we only study relation of these four quantities velocity, distance, time and acceleration relationship in kinematics.
3 Dynamics here we study the cause of motion, how start motion, how stop motion and cause of changing direction, we study all this in dynamics .
hence all this three are related to motion and study in motion, body not moving, body moving, the cause of body moving and this is know as mechanics one branch of physics.
Now come to motion what is motion ? one object at a certain position and after some time the object shifted its position to other point suppose object is initially at point A and after certain interval of time it shifted its position to point B.
The process of changing its position from point A to B is called motion.
Now we have to Study REST AND MOTION.
Infect in our nature there is no any body or any particle which is at rest this is the fact we all thought we are standing on ground but in fact earth is moving the we are also moving with earth, if we suppose earth is at rest which is wrong because earth is rotating around sun so earth is not at rest and we are also not at rest then we thought sun is at rest then answer is big no sun is not at rest sun is moving along with its family planets and hence whole Galaxy is moving then who is at rest then answer is nobody even inside your body parts all are in motion like lungs, heart, blood, breath, kidney so you will not find anything which is at rest if all are moving then how we will calculate about any body or particle motion that this body was initially at rest whenever nothing is at rest how we will imagine for rest this is big question so for this we made a process any body with respect to its surrounding if its distance is changing then body is called under motion and if with respect to surrounding the distance of body is not changing then body is called at rest suppose your are sitting in your room and watching TV in room there are some other object like sofa, refrigerator you are sitting at your place after 1 minute you observe the distance from TV, sofa and refrigerator to your position is same means your position is not changing with respect to surrounding then of course you are in rest with respect to surrounding around you then you are at rest hence in physics we accept the body at rest when body is not changing its position with respect to its surrounding otherwise you can objection any body is not at rest because earth is moving so at rest is a relative term with respect to any other point or object reference suppose in a moving train two person are sitting in front of each other in a compartment so 2nd person is at rest with respect to first person because distance between them is not changing while train is moving but when we asked a person standing on platform he observe both the person sitting in train are moving hence with respect to person on platform they are moving so motion always describe with respect to some frame of reference that is relative to any point or object and its state will be different with respect to different point or object relation like i am father or son then the answer is i am son in relation of my father and i am father in relation of my son or daughter so similar fashion motion is relative now we need to study types of motion.
Types of Motion
1 (1-D) here one D stand for one dimension motion its second name is (rectilinear motion) , dimension means direction, when a particle moves in a straight line then it is called one dimension motion in our Cartesian coordinate system graph we have three dimension that are called x, y,z direction, we don’t named top, down, left, right,north, east, west, south simply fixed x,y,z direction see below figure.
↑ positive x
↙ 0→ → →→→→→→→→→→→→ x
↙ negative y
here 0 is origin fixed positive x, positive y, positive z direction opposite side is taken as negative for all three hence total is 6 direction in Cartesian coordinate system is facility to take any direction x, y,z not compulsory shown x direction is fixed for x direction we can choose any direction as x but compulsory is all three direction x,y,z are perpendicular to each other means angle between them is 90 degree if we will rotate one direction then all will rotate hence take a particle is initial at point A and after some time its reach at point B shown in figure.
here we see that only x coordinate of particle is changing no any change in distance of y and z coordinate hence this is called one dimension ( 1-D) motion if particle moves in any of a single direction it is (1-D) motion hence in one D motion particle will always moves in a straight line this is thumb rule. example any body moving on the ground in a straight line is (1-D) motion.
2 (2-D) Motion motion in a plane when two dimension are changing simultaneously then motion is called (2-D) motion example projectile is two dimension motion see the figure below.
↑ particle moving
here we see that particle is moving in xy plane changing its x and y coordinate both simultaneously hence particle has two direction motion x and y.
3 (3-D) Motion when all three coordinate are changing x,y,z then this type of motion is called (3-D) motion because particle is moving in all thee direction when a bird is flying in space, aeroplan flying in space,when footballer is running on the ground then it is (2-D) motion but when he jump to hit the ball in above the ground then it is (3-D) motion understand concept how projectile motion is (2-D) motion whenever ball is projected with some angle in space then ball moves in a particular line not moves front and back so it is plane motion and (2-D) motion but when bird fly it can move back and front so it is a space motion hence all space motion is (3-D) motion now after this we made other classification of motion which can be in a line, circle or in a oscillation to and fro that is different types of classification .
1 Rectilinear and translatory when a body is moving in a line is there any difference between Rectilinear and translatory motion answer is yes difference, when the moving body is a point very small and moving in a straight line of a large distance compare to body size then it is called rectilinear motion hence in rectilinear point moves in a straight line then what is translatory ? answer is when our object is not point size it is a big size object is moving from one point to other point like our table is move a distance of 3 m this body is made by different group of particles so it is called rigid body now rigid body is that body which internal distance of particle is not change when it is move from one point to other point suppose the table is moved with speed of 1 m/s so every particle of table will move with a speed of 1 m/s and their internal distance of particle is fixed with each other particle not change and move each particle same distance parallel to each other this type of motion is called translatory motion. see below this object is moved from point A to point B. this is called translatory motion.
2 Circular or Rotational Circular motion when a point moves in such a way that it is always at a fixed distance from a given point (center ) this is called circular motion here important is single point.
Rotational motion when a rigid body rotate about a straight line (axis) such that all the particles make circular motion with similar angular velocity with different radii is called rotational motion example of this is rotating fan.
Circular motion Rotational motion
Oscillatory motion this is such a motion a particle moves such that to and fro motion about a mean position is called oscillatory motion figure is given below.
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