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# chapter4.1-44_slide - 9/20/2009 Chapter 4. The Laws of...

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9/20/2009 1 Chapter 4. The Laws of Motion Aristotle (384 BC 322 BC) Isaac Newton (1643 1727) Chapter 2 and 3 deal with description of motion: Relationship between displacement, velocity, and acceleration - Kinematics Starting from this chapter, we will ask Why do things move and how? Relationship between the motion of objects and the forces acting on them - Dynamics Concepts: - force, mass, acceleration, action and reaction Laws: - Newton’s three laws and - Newton’s law of universal gravitation

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9/20/2009 2 Aristotle: First theory of motion (wrong theory, by the way) - Everything is in a state of rest until you give it a push. - Makes perfect sense, but unfortunately wrong - Widely accepted until the 17 th century Newton: - Force is NOT the cause of motion, but it causes changes in motion What are forces, anyway? What are forces? Examples pull push Contact forces Gravitational force Magnetic force Electrical force Field Forces: No direct physical contact PHY 102
9/20/2009 3 Force is a vector quantity Maybe contact force or field force - Contact forces result from physical contact between two objects - Field forces act between disconnected objects However, only field forces are fundamental. - At the microscopic level, contact forces are also field forces Four fundamental forces in nature - Strong nuclear force (subatomic particles) - Electromagnetic force (between charges, magnets) - Weak nuclear force (radioactive decay) - Gravitational force (between masses) Newton’s first law of motion: An object moves with a velocity that is constant in magnitude and direction, unless acted on by a nonzero net force. Before 17 th century, people believed that the natural state of matter was the state of rest . Galileo, however, concluded that the natural state of matter is to continue its original state of motion. Newton formalized Galileo’s idea into Newton’s first law of motion. Sir Isaac Newton (1642 1727) Formulated basic concepts and laws of mechanics Formulated the law of Universal Gravitation Invented Calculus Investigated light and optics

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9/20/2009 4 Things tend to stay the way they are, Tend to keep on doing what they are doing
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## This note was uploaded on 01/02/2010 for the course PHY 101 taught by Professor Pralle during the Spring '08 term at SUNY Buffalo.

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chapter4.1-44_slide - 9/20/2009 Chapter 4. The Laws of...

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