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Relate friction and gravity to each of Newton's three laws of motion...examplesthank...

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sheriff97 | Student, Grade 9 | (Level 1) Honors

Posted September 20, 2012 at 4:27 AM via web

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Relate friction and gravity to each of Newton's three laws of motion...examples

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ncchemist | eNotes Employee

Posted September 22, 2012 at 12:56 PM (Answer #1)

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I will write out each of Newton's laws of motion and handle each one individually:

1: A body at rest tends to stay at rest and a body in motion tends to stay in motion (in the absence of external forces).  Gravity relates to this as a force acting on a falling object in a vacuum.  Gravity is a constant force and as long as the falling object has enough airspace to continue falling it will continue to fall at a constant acceleration.  Friction comes into play with wind resistance.  The atmosphere will provide friction against a falling object in real life and will eventually halt the acceleration of gravity to a constant velocity (terminal velocity).

2: Force is equal to mass times acceleration (F=ma).  Gravity is involved here as a regular constant force.  Its acceleration is constant so it will act as a constant force on an object with any given constant mass.  Friction is also a force against an object.  But it will be a negative force against other forces since it is acting to deccelerate moving objects (negative acceleration times a mass equals a negative force).

3: For every action there is an equal and opposite reaction.  Gravity is a constant force for every object resting against a surface (a book sitting on a table as an example).  That means that since the book is exerting a force F on the table due to gravity, the table is exerting a force -F against the book.  I do not see how friction really applies here.

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