motion

MOTION
Movement, or motion, is the state of changing something's position--that is, changing where something is. A flying bird or a walking person are moving, because they change where they are from one place to another. There are many kinds of science and math related to movement.

For example, thanks to Albert Einstein, we know that all position is relative. This means that everything's position depends on where they exist in relation to other things. For example, a ball is 5 feet away from a box, 3 feet away from a chair, and a foot away from a table. According to Einstein, the ball's position means how far the ball is from other things, so by telling you how far the ball was from other things, I told you its position. An object's movement is also relative. Its movement depends on where it is in relation to other things and where it's going to in relation to other things.

There are many things involved in movement, such as speed, velocity, acceleration, gravity, magnetic attraction and repulsion, friction, and inertia. Also, work is needed to produce movement.

Newton's laws of motion
__//**Isaac Newton**//__ (1642-1727), the father of the dynamics, – the study of motion – developed three sets of laws that are believed to be true because the results agree with the laws he produced.


 * First Law**

If a body is at rest it remains at rest or if it is in motion it moves with uniform velocity until it is acted on by a resultant force. (Duncan, 1995)

In other words, the first law says that an object that is not moving or moving in a constant speed in a straight line, will stay like that until something pushes it or blocks its path. As we all know, nothing in the visual world ever stays in constant speed, but the object itself is moving at constant speed, while a force is stopping it from moving at constant speed, friction.

However, in space, an object can move in a constant speed as long as it does not get close to any other objects, and stays in open space. This is why rockets use less fuel in space than they do getting to it.


 * Second Law**

In other words, force is equal to mass times acceleration.

F = ma

This law provides the definition and calculation of force through mass and acceleration.

To help the understanding of this concept, replace force with weight. Weight is a force that we feel on Earth, caused by gravity and our mass. Since gravity is calculated using the units of m/ s2 therefore it is an acceleration constant. We could come to the conclusion that:

W = mg


 * Newton's Third Law**

__//Newton's third law is://__

For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object. The direction of the force on the first object is opposite to the direction of the force on the second object. Forces always come in pairs - equal and opposite action-reaction force pairs.

A variety of action-reaction force pairs are evident in nature. Consider the propulsion of a fish through the water. A fish uses its fins to push water backwards. But a push on the water will only serve to accelerate the water. Since forces result from mutual interactions, the water must also be pushing the fish forwards, propelling the fish through the water. The size of the force on the water equals the size of the force on the fish; the direction of the force on the water (backwards) is opposite the direction of the force on the fish (forwards). For every action, there is an equal (in size) and opposite (in direction) reaction force. Action-reaction force pairs make it possible for fish to swim.

Consider the flying motion of birds. A bird flies by use of its wings. The wings of a bird push air downwards. Since forces result from mutual interactions, the air must also be pushing the bird upwards. The size of the force on the air equals the size of the force on the bird; the direction of the force on the air (downwards) is opposite the direction of the force on the bird (upwards). For every action, there is an equal (in size) and opposite (in direction) reaction. Action-reaction force pairs make it possible for birds to fly.

Consider the motion of a car on the way to school. A car is equipped with wheels which spin backwards. As the wheels spin backwards, they grip the road and push the road backwards. Since forces result from mutual interactions, the road must also be pushing the wheels forward. The size of the force on the road equals the size of the force on the wheels (or car); the direction of the force on the road (backwards) is opposite the direction of the force on the wheels (forwards). For every action, there is an equal (in size) and opposite (in direction) reaction. Action-reaction force pairs make it possible for cars to move along a roadway surface.