handout_forces - Reviewer for Forces, Energy and Momentum...

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.AKGTapia Physics Division, IMSP, CAS, UPLB College, Laguna Reviewer for Forces, Energy and Momentum Mechanics-study of the relationship among matter, motion, and force. 2 Branches of Mechanics 1. Kinetics -deals with motion 2. Dynamics -deals with the causes of motion PART I Newton’s Laws (NL) Can explain motion Note: NL are applicable only on Inertial Frames - frame at rest or moving with constant velocity . Mass -An intrinsic property of an object that measures its resistance to acceleration. Measure of inertia (reluctance to change in velocity) Force -Push or pull. The influence on an object that causes the object to change its velocity or to accelerate. Described by the 1st and 2nd Laws of Newton First Law: The Law of Inertia A body continues in its initial state of rest or motion with uniform velocity unless it is acted on by an unbalanced, or net external, force. = F F net Second Law: Law of Mass and Acceleration The acceleration of an object is inversely proportional to its mass and directly proportional to the net external force acting on it. m F net = a Third Law: Law of Interaction Forces always occur in pairs. If object A exerts a force on object B, and equal but opposite force is exerted by object B on object A. Contact Forces Observed between macroscopic objects, such as contact forces of support , friction , and those exerted by springs and strings Arise from the basic electromagnetic force Restoring Force Restoring a body to its initial configuration Hooke’s Law: F s =-kx, the force exerted by the spring Frictional Force Force which opposes the motion of a body In general, η μ = f where μ is the coefficient of friction and depends on the nature of the contact surfaces η is the normal force and f is the frictional force Note: Subscript s and k for f or μ indicate static and kinetic, respectively. x Static friction-frictional force present for bodies at rest x Kinetic friction-frictional force present for bodies moving. μ s > μ k Ideally, frictional force does not depend on the area of contact but on the normal force and coefficient of friction. Solving Problems using Newton’s Laws
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This note was uploaded on 10/03/2009 for the course COL PHYS 81 taught by Professor Tapia during the Spring '09 term at University of Santo Tomas.

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handout_forces - Reviewer for Forces, Energy and Momentum...

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