Physical concepts force

Forces make things happen. Forces speed things up and forces slow things down. There are attractive forces and repulsive forces. An attractive force pulls magnetic decals to the refrigerator door and pulled Comet Shoemaker-Levy into the churning surface of the planet Jupiter a repulsive force pushes two strips of scotch tape apart after they are stripped from a table top. In the arsenal of physical concepts, force is one of the most important. 

Dimension arises from our desire to quantify our perceptions. We describe a sensory perception with a physical concept. Force we experience as impact. If a grocery cart bumps a car in the parking lot, the car may suffer a scratch or small dent. If a car collides with another car at a city street intersection, the damage to both cars will be significant. If an 18-wheel truck collides with a car on an interstate or motorway, the result will be catastrophic. From this information, we know that force, or impact, involves mass and acceleration. Thus, to quantify force, we need to specify the dimensions mass, length, and time. When we make such a specification, we convert the physical concept of force into the physical quantity of force. Thus to quantify a physical concept, we first determine a descriptor that best characterizes it, that produces a valid physical quantity. Therefore a physical quantity represents a qualitative description of a physical concept. In other words, a physical concept attains meaning only if its descriptors can be measured. Those descriptors are dimensions. 

In the first chapter several traditional types of physical models were discussed. These models rely on the physical concepts of energies and forces to guide the actions of molecules or other species, and are customarily expressed mathematically in terms of coupled sets of ordinary or partial differential equations. Most traditional models are deterministic in nature— that is, the results of simulations based on these models are completely determined by the force fields employed and the initial conditions of the simulations. In this chapter a very different approach is introduced, one in which the behaviors of the species under investigation are governed not by forces and energies, but by rules. The rules, as we shall see, can be either deterministic or probabilistic, the latter leading to important new insights and possibilities. This new approach relies on the use of cellular automata. 

At Georgia Southern we begin the year of physical chemistry with a review of basic, relevant physics concepts including kinetic energy, force, pressure, the ideal gas law, and the units that describe them. This leads into a rather standard... 

The application of DLVO-theory to explain the experimental TI(/i) isotherms in the range of small thickness values, in particular for NBF, is even more inconsistent, since in this case it is necessary to account for the short-range interaction forces and other physical concepts are required. That is why we believe that the approach according to which the NBF represents an ordered bilayer system with strongly expressed short-range molecular interactions is the most promising (see Section 3.4.1 and 3.4.4). 

Force Fields. The basic assumption underlying molecular mechanics is that classical physical concepts can be used to represent the forces between atoms. In other words, one can approximate the potential energy surface by the summation of a set of equations representing pairwise and multibody interactions. These equations represent forces between atoms related to bonded and nonbonded interactions. Pairwise interactions are often represented by a harmonic potential - 6q) ]... 

Besides the physical concepts leading to eqs. (15) to (18), we need one more concept, and that is the law of conservation of mass. Applied to porous catalyst in a steady state of reaction, this law says that the total mass of matter which flows into a pellet or pore (or any region thereof) must equal the mass that flows out. For example, in Fig. 4 the mass of reactants plus products which flows across the plane at M must equal the mass of these which flows across the plane at N. The most important special case is the usual one encountered for catalysts of small pore size in reactors operating at low pressure drops across the reactor. For such catalysts the Poiseuille flow forced through the pellet by the reactor pressure drop will be negligible so that there will be no net transport of mass... 

Understand and use important physical concepts, such as force, work, energy, momentum, and mechanical equilibrium... 

Ostwald merged the two approaches there is not a direct physical catalytic force or action nor a direct modification of the chemical bonds but the thermodynamic of the whole system is changed with new ways of lower free energy in the chemical transformation (Ostwald, 1902). Substantially the actual conception of the phenomena. 

Dimensions come in two varieties fundamental and derived. Fundamental dimensions form a basic set of quantifiers for describing a physical concept. Derived dimensions arise from our study of Nature many observations of Nature require us to combine fundamental dimensions to quantify them. Chasing mastodons across the prairie may have suggested the physical concept of speed to one of our ancestors. Speed, or velocity, is described by the physical quantity of [L]/[T] or [LT ]. [LT ] is a derived dimension. Using the fundamental dimensions [LMT], we derive force [F] via Newton s second law, namely... 

Review basic physical concepts relevant to the study of soft matter, including basic thermal physics, intermolecular forces, and the mechanical properties of materials. 

---