Motion

Change in the position of an object with respect to time is the motion of an object is the motion of an object. Motion is one of the most important part of branch of physics called mechanics. Everybody on the Earth moves. The movement might be slow or very very slow. If we are standing on earth then earth moves around the Sun and Sun moves around the galaxy. It means that the movement of a body never stops.
To have a motion of an object or to change its motion, the force should be acted on an object. When some Physicists observe that, how an object moves? , they use some basic terms like the speed or velocity with which an object moves, the mass of an object which also affects on motion of object, forces acting on an object, acceleration(rate of change of velocity with respect to time), energy and the work.
Some basic equations related to motion:
v(velocity) = s(displacement)/ t(time)
a(accelaration) = dv(changes in velocity) / dt(changes in time)
F(force) = ma where, m=mass
Types of Motion:

• Uniform motion In this type of motion the direction and the speed of an object are the same and do not change with respect to time. In such case, the object moves in the same direction and travels through equal distance in equal interval of time, however these intervals may be small.  Obviously, when the object is in uniform motion, its instantaneous velocity (it is average velocity as the time-interval t becomes extremely small) is the same everywhere along its path. Also its average velocity is the same as its instantaneous velocity.
  
• Variable motion In this type of motion the direction or speed changes with respect to time. In this displacement of an object varies from instant to instant, either increasing or decreasing.
  
• Periodic motion
  The motion that repeats and always returns to its original initial position is called periodic motion. Periodic motion repeats in equal interval of time. Examples of periodic motion are a rocking chair, a bouncing ball, a vibrating guitar string, a swinging pendulum, and a water wave, the motion of the Earth in its orbit around the sun.