motion,types of motion,uniforn and non uniform circular motion

MOTION

In physics, motion means a continuous change in the position of a body relative to a reference point, as measured by a particular observer in a particular frame of reference. Until the end of the 19th century, Isaac Newton's laws of motion, which he posited as axioms or postulates in his famous Principia were the basis of what has since become known as classical physics. Calculations of trajectories and forces of bodies in motion based on Newtonian or classical physics were very successful until physicists began to be able to measure and observe very fast physical phenomena.
At very high speeds, the equations of classical physics were not able to calculate accurate values. To address these problems, the ideas of Henri Poincaré and Albert Einstein concerning the fundamental phenomenon of motion were adopted in lieu of Newton's. Whereas Newton's laws of motion assumed absolute values of space and time in the equations of motion, the model of Einstein and Poincaré, now called the special theory of relativity, assumed values for these concepts with arbitrary zero points. Because (for example) the special relativity equations yielded accurate results at high speeds and Newton's did not, the special relativity model is now accepted as explaining bodies in motion (when we ignore gravity). However, as a practical matter, Newton's equations are much easier to work with than those of special relativity and therefore are more often used in applied physics and engineering.
In the newtonian model, because motion is defined as the proportion of space to time, these concepts are prior to motion, just as the concept of motion itself is prior to force. In other words, the properties of space and time determine the nature of motion and the properties of motion, in turn, determine the nature of force.
In the special relativistic model, motion can be thought of as something like an angle between a space direction and the time direction.
In special relativity and Euclidean space, only relative motion can be measured, and absolute motion is meaningless.
An object is in motion when its distance from another object is changing.Whether the object is moving or not depends on your point of view. For example, a woman riding in a bus is not moving in relation to the seat she is sitting on, but she is moving in relation to the buildings the bus passes. A reference point is a place or object used for comparison to determine if something is in motion. An object is in motion if it changes position relative to a reference point. You assume that the reference point is stationary, or not moving.

Types of Motion
A pendulum exhibits Simple harmonic motion, or, motion that is constantly being accelerated towards a midpoint. Other types of motion include Linear motion and Reciprocation. Examples of naturally occurring motion are Brownian Motion (the movement of particles), and the orbits of planets.

UNIFORM CIRCULAR MOTION
Uniform circular motion describes motion in which an object moves with constant speed along a circular path.

ACELERATION & UNIFORM VELOCITY
Since the velocity is tangent to the circular path, no two velocities point in the same direction. Although the object has a constant speed, its direction is always changing. This change in velocity is caused by an acceleration, whose magnitude is (like that of the velocity) held constant, but whose direction is always changing. The acceleration points radially inwards (centripetally) and is perpendicular to its velocity. This acceleration is known as centripetal acceleration.

Non-uniform circular motion

Non-uniform circular motion is any case in which an object moving in a circular path has a varying speed. Some examples of non-uniform circular motion include a roller coaster, a vertical pendulum, a car riding over a hill, and much more. All of these situations include an object traveling at different speeds in a circular path. For the roller coaster, its cars travel faster during its trip down than its trip up. The pendulum’s mass swings in a semicircle in which its trip up slows down to 0 m/s and comes back down. A car riding over a hill will experience different speeds at different points of the hill.

Differences from uniform circular motion
The way to express non-uniform circular motion is not that different from the techniques used in calculating uniform circular motion. In uniform circular motion, the magnitude of the tangential acceleration is always equal to zero assuming speed remains constant. The radial acceleration in uniform circular motion is equal to the centripetal acceleration, which is towards the center of the circle. In non-uniform circular motion, the radial acceleration is the same and equal to towards the center of the circle. What’s different is the tangential acceleration, since speed is non-zero and changing.
Since there is a non-zero tangential acceleration, there are forces that act on an object in addition to its centripetal force (composed of the mass and radial acceleration). These forces on the object include forces such as weight, normal force, and other forces acted on the object due to the environment it is in such as friction.