Classical mechanics

Mechanics is one part of physics. It says what happens when forces act on things. There are two parts of mechanics. The two parts are classical mechanics and quantum mechanics. Classical mechanics is good most of the time. It is good to say what happens about most things we can see. Some of the time, for example when the things are too small, classical mechanics is not good. Then we need to use quantum mechanics.

Newton's Three Laws

Newton's three laws of motion are important to classical mechanics. Isaac Newton made them.

The first law says that, if there is no external force, things that are stopped will stay stopped, and things that are moving will keep moving. Before, people thought that things stopped if there was no force. Often, people say, Objects at rest tend to stay at rest, and objects in motion tend to stay in motion, unless acted upon by an outside force.

The second law says how a force moves a thing. The force on a object equals the change in momentum.

The third law says that if one thing puts a force on another thing, the second thing also puts a force on the first thing. For example, if you jump forward off a boat, the boat moves backward. Often, people say, For every action there is an equal and opposite reaction.

External links

Science aid: Newton's laws of motion
The Engineering Wiki's shorter page with the same title - engineers may improve it!
Newtonian Physics - an on-line textbook
Motion Mountain - an on-line textbook
Trajectory Video - video clip showing exchange of momentum
Newtonian attraction for three Planets (Mathcad Application Server)
Gravity - Newton's Law for Kids

Physics

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Newton's Three Laws

External links