chapter4.key - Chapter 4 Forces and Mass Classical...

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Unformatted text preview: Chapter 4 Forces and Mass Classical Mechanics does not apply for very tiny objects (< atomic sizes) objects moving near the speed of light Newtons First Law If the net force ! F exerted on an object is zero the object continues in its original state of motion. That is, if ! F = 0, an object at rest remains at rest and an object moving with some velocity continues with the same velocity. Contrast with Aristotle! Forces Usually a push or pull Vector Either contact or field force Contact and Field Forces Fundamental (Field) Forces Types Strong nuclear force Electromagnetic force Weak nuclear force Gravity Strong Nuclear Force QCD (Quantum chromodynamics) confines quarks by exchaning gluons Nuclear force: binds protons and neutrons by exchanging pions Electromagnetic Forces Opposites attract, like-signs repel Electric forces bind electrons in atoms Magnetic forces arise from moving charges Weak Nuclear Force Involves exchange of heavy W or Z particle Responsible for decay of neutrons Gravity Attractive force between any two bodies Proportional to both masses Inversely proportional to square of distance F = G m 1 m 2 r 2 Inertia (Newtons First Law) Tendency of an object to continue in its original motion Mass A measure of the resistance of an object to changes in its motion due to a force Scalar SI units are kg Newtons Second Law Acceleration is proportional to net force and inversely proportional to mass. ! F ! = m ! a Units of Force SI unit is Newton (N) US Customary unit is pound (lb) 1 N = 0.225 lb F = ma 1 N = 1 kg ! m s 2 Weight Weight is magnitude of gravitational force w = mg w = G M earth m r 2 g = GM earth R earth 2 weight mass Weight vs. Mass Mass is inherent property Weight depends on location Newtons Third Law Single isolated force cannot exist For every action there is an equal and opposite reaction Force on 1 due to 2 !...
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chapter4.key - Chapter 4 Forces and Mass Classical...

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