newtons law of motion

Every body will persist in its state of rest or of uniform motion (constant velocity) in a straight line unless it is compelled to change that state by forces impressed on it. This means that in the absence of a non-zero net force, the center of mass of a body either is at rest or moves at a constant velocity.

that is Newton's first law of motion. But what does it mean?

This law states that if theresultant force(the vector sum of all forces acting on an object) is zero, then the velocity of the object is constant. Consequently, an object will always stay at rest unless an unbalanced is acted upon it, and a moving object will not change its velocity unless an unbalanced force is acted upon it.an unbalanced force is when a number of forces act on a body simultaneously and the resultant of these forces is zero then the forces are said to be balanced. Equal forces acting on an object in opposite direction. Is when two forces are applied on an objectin a different direction.

There are many exellent examples to depict Newton's first law of motion at work, such as when a pilot changes the throttle of the aeroplane, it shows 'a moving object will not change its velocity unless an unbalanced force is acted upon it. similarly, the first law can be shown as something as simple as kicking a soccer ball or even sliding a book on the floor.

subconciously, Newton's first law is seen everyday.

Centroiles

These are part of a cell, only present in the animal cell, are paired organelles located together near the nucleus in the centrosome, which organises these centroiles. each centroile consists of 3x9 microtubules, arranged in a ring.

these play a notable role in cell division.During interphase of an animal cell, the centrioles and other components of the centrosome are duplicated, though scientists are not yet sure how this duplication takes place. At first the two pairs of centrioles remain in close proximity to each other, but as mitosis initiates, the original centrosome divides and the pairs are split up so that one set of centrioles is located in each of the new microtubule-organizing centers. These new centers radiate microtubules in star-shaped clusters known as asters. As the asters move to opposing poles of the cells, the microtubules, with the help of the centrioles, become organized into a spindle-shaped formation that spans the cell.these fibres act as guides for the alignment of the chromosone that seperate later during cell division.

Though centrioles play a role in the mitosis of animal cells, plant cells are able to reproduce without them. Researchers have, therefore, been very interested in determining exactly how important the organelles really are. Studies have shown that certain animal cells, particularly female gametes (oocytes), can successfully divide even when their centrioles are destroyed. Some investigators have also found, however, that the absence of centrioles in animal cells is associated with an increased number of divisional errors and substantial delays in the mitotic process, especially before chromosome segregation. Consequently, it has been suggested that centrioles evolved as a refinement of the cell, making mitosis a much more efficient and less error-prone process.

This is a picture of centroiles in animal cell mitosisat the top/\