PHYS 195 chapter 5 (part one)

# PHYS 195 chapter 5 (part one) - Newtons laws 09/24/2010...

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09/24/2010 Physics 201, Spring 2006, U.Wisconsin 1 Newton’s laws

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09/24/2010 Physics 201, Spring 2006, U.Wisconsin 2 Contact and Field Forces Electromagnetic force Gravity
09/24/2010 Physics 201, Spring 2006, U.Wisconsin 3 Dynamics due to force Isaac Newton (1643 - 1727) published Principia Mathematica in 1687. In this work, he proposed three “laws” of motion: Law 1 : An object subject to no net external force is at rest or moves with a constant velocity a M F F i i net r r r = = Law 2 : For any object, Law 3 : Forces occur in pairs: (For every action there is an equal and opposite reaction.) a b b a F F , , r r - =

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09/24/2010 Physics 201, Spring 2006, U.Wisconsin 4 Newton’s First Law a The motion of an object does not change unless it is acted upon by a net force . • If v =0 , it remains 0 • If v is some value, it stays at that value a Another way to say the same thing: • No net force velocity is constant acceleration is zero
09/24/2010 Physics 201, Spring 2006, U.Wisconsin 5 Question 1 An airplane is flying from LAX airport to SAN. Many forces act on the plane, including weight (gravity), drag (air resistance), the thrust of the engine, and the lift of the wings. At some point during its trip the velocity of the plane is measured to be constant (which means its altitude is also constant). At this time, the total force on the plane: 1. is pointing upward 2. is pointing downward 3. is pointing forward 4. is pointing backward 5. is zero lift weight drag thrust

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09/24/2010 Physics 201, Spring 2006, U.Wisconsin 6 Newton’s Second Law a The acceleration a of an object is proportional to the net force F NET acting on it. a The constant of proportionality is called “mass” , denoted M . » This is the definition of mass . » The mass of an object is a constant property of that object, and is independent of external influences. a A vector equation: » F net, x = Ma x » F net, y = Ma y a M F net r r = Units: [M] = kg [F] = [M] [a] [F] = kg-m/s 2 1 Newton (N) 1 kg-m/s 2
09/24/2010 Physics 201, Spring 2006, U.Wisconsin 7 Mass or Inertia Mass (M) is the property of an object that measures how hard it is to change its motion . Importance of mass

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## This note was uploaded on 01/04/2011 for the course PHYS 195 taught by Professor Anderson during the Fall '07 term at San Diego State.

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PHYS 195 chapter 5 (part one) - Newtons laws 09/24/2010...

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