Newton's Laws

Newton's Laws

Dynamics is the study of how bodies interact with one another; it answers the question, "Why does the motion of a ball change?"
Isaac Newton expressed a set of three rules which allow one to predict the result of interactions between objects. These are known as Newton's Three Laws of Motion.
The quantities which these rules govern are
- acceleration (m/s^2)
- mass (kg)
- force (kg-m/s^2)
Inertia is a property of objects: the degree to which they resist changes in their motion. It turns out that the inertia of an object is directly proportional to its mass: the more massive it is, the harder one has to push to move it.
Weight is the force exerted downwards by a body in a gravitational field. It is not the same as mass.

Newton's First Law:

     A body at rest stays at rest, and a body in motion continues
     in motion with constant velocity, unless some external force
     acts upon it.

Newton's Second Law

     The acceleration of an object is directly proportional to the
     force applied to it, and inversely proportional to its mass.

In other words,

              F = ma

Newton's Third Law

 
     If a body exerts a force on a second body, then the second
     body exerts an equal and opposite force on the first.

But note that the result of these opposing forces depends on the mass of each body.

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