|MadSci Network: Physics|
Newton's Three Laws of Motion and my interpretation. FIRST LAW: Consider a "body" on which no net force acts. If the body is at rest; it will remain at rest. If the body is moving with a constant velocity, it will continue to to do so. MEANING: In some way of looking at the body there is no acceleration. The body will continue to do what it is already doing (sitting still, sliding...). A force is needed to change the velocity of the body. In everday life, friction usually makes the FIRST LAW hard to observe. If I slide a book along a table, the book will eventually stop. A rolling ball is a better example. The ball will roll along in a given direction until either it hits something (like a wall or a bump) or until it gets to a slope of some sort and changes direction. The change of direction at a slope results from gravity acting upon the ball. SECOND LAW: Force = mass * acceleration. MEANING: Just the specifics of the FIRST LAW. Mass (or inertia) is the body's ability to resist change. THIRD LAW: Usually stated something like: For every action there is an equal but opposite reaction. MEANING: If I am standing on the ground, my body pushes on the earth. The earth pushes back upon me with the same force that I apply but in the opposite direction. My force is my weight in the downward direction. The earth pushes up with a force of the same amount. I hope this clears up some of the confusion. Sincerely, Tom "Physics Attorney" Cull
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