Studied by 15 people
Bosons: photons, W/Z particles, gluons and gravitons
Fermions
Composed of two "up" quarks, one "down" quark
Positive ( + ) charge
Mass = 1.672 * 10^-27 kg
Composed of two "down" quarks, one "up" quark
Neutral ( 0 ) charge
Mass = 1.674 * 10^-27 kg
Leptons
Negative ( - ) charge
Mass = 9.109 * 10^-31 kg
Weak attractive force
Infinite range
Acts within a field established by collections of baryonic matter
A strong attractive or repulsive force (dependent on charge)
Infinite range
Acts within a field established by stationary or moving charged particles
Moving charged particles produce electromagnetic waves.
◊ The particle equivalent of electromagnetic wave energy is quantized as photons.
Within the nucleus of an atom, electrostatic repulsive forces exerted between protons destabilizes the cohesion of larger nuclei.
Strong nuclear force is a very strong attractive force exerted between nucleons over extremely short range.
Exerted by bosons called gluons
Electrostatic repulsive forces between protons and strong nuclear force between nucleons act in equilibrium within atomic nuclei.
The process of radioactive decay of unstable atomic nuclei is mediated by the week nuclear force.
Extremely short range
Exerted by weak bosons.
Macroscopic object interactions are the result of microscopic electromagnetic force field interactions.
The interaction electromagnetic force field range between macroscopic objects can be as small as an angstrom (10⁻¹⁰m), so objects appear to touch or come into “contact”.
Gravitational force, electromagnetic force, strong nuclear and weak nuclear forces all occur at range or within a “field”.
Some models relate interacting field density to an exchange of virtual particles, but that will not be addressed in the scope of this course.
Velocity changes can be the result of a change in the magnitude of a velocity.
Velocity changes can be the result of a change in the direction of a velocity.
A net force is required to alter magnitude and or direction of a particle.
Materials are composed of arrays of atoms linked together by electromagnetic forces.
External electromagnetic forces may displace the relative position of individual atoms, while the material remains intact.
This alteration of composite atom position is defined as deformation.
Some materials have the capacity to return to initial configurations after an external force is discontinued, while others experience permanent deformation.
A particle that is “stationary” within the context of its surroundings, or moving with a uniform velocity is defined to be in an inertial frame of reference.
A particle within an inertial frame of reference is defined to have no net force exerted upon it.
Consider a particle within closed container. If the container particle system is moving with a uniform velocity, from the point of view of the particle – the particle is stationary, with no reference points or net force evidence to indicate that it is within a moving system.
Inertial reference frames are usually hypothetical constructs for simplification of problem solving and conceptual interpretation.
The net force exerted on a particle in an inertial frame of reference is defined to be zero.
Any particle that is experiencing a change in velocity (a≠0) is in a non-inertial frame of reference.
A particle within a non-inertial frame of reference is defined to be experiencing a net force.
All particles on the surface of the earth are in a non-inertial frame of reference because the Earth is revolving on its axis(1/day), translating on an elliptical path around the sun (1/365.25day), translating on an elliptical path around the Milky Way galaxy(1/250my), and accelerating through the universe.
Gravitational forces are exerted at all scales and dominate at the largest distances and mass scales.
Electromagnetic forces are exerted at all scales, and for our purposes are most relevant at contact force scales.
Strong and weak nuclear forces are exerted at very small scales and are not considered in great depth in this course.
