Linear or tangential velocity is the instantaneous or average rate of change of position or displacement of a rigid body. It is speed of a body in a specified direction measured in meters per second (ms-1). Angular velocity is the rate at which a rigid body or point rotates around a fixed axis, which is …
Author Archives: Brian Hopkins
Vector field
A plot of the relationships among two or more variables in terms of the changes that are expected from any set of initial stating points. In physics, it stands, for example, for a gravitational or magnetic field in which the magnitude and direction of the vector quantity are one-valued functions of position . See Design …
Vector
In statistics, a set of ordered values in a column (or row) of a matrix, or a matrix with only one column or row. In mathematics and physics, it includes a quantity for which the magnitude and direction must be stated. Examples of vector quantities are force and velocity, the latter being different from speed …
Vasoconstriction
Narrowing of the blood vessels. Nicotine, for example, elicits vasoconstriction in placental and fatal vascular beds, reducing oxygen and nutrients accessible to the fetes, and thus increasing the risk for intrauterine growth retardation . See Carboxyhemoglobin (CoHb), Environmental tobacco smoke (ETS), Hypoxia, Intrauterine growth retardation (IUGR), Nicotine
Variance within
The variance of the individuals‚aa raw scores in an analysis of variance. See Intra-individual differences, Variance between
Variance between
The variance of the means in an analysis of variance factor . See Variance within
Variance-covariance matrix
A symmetric square matrix with variances of the variables in its main diagonal and covariances of pairs of variables in its off-diagonal cells. See Covariance, Compound symmetry, Greenhouse-Geisser epsilon, Pattern of variances and covariances
Variable
An attribute or characteristic that can change or vary or be expressed as more than one value or in various values or categories. The opposite of a variable is a constant. See Concept, Confounding variable, Error score, Experimental method, Ordinal variables, Parameter (statistics)
Variable-centered approaches
A research strategy that analyses the effect of specific variables (e.g., age, maternal alcohol intake) on children’s current or later development. See Child psychology, Longitudinal studies, Longitudinal studies, Person-centered approaches
van der Waals forces
Named after Johannes Diderik van der Waals (1837-1923), the simplest definition is that they are weak attractive forces that contribute to bonding between molecules or atoms. They are called weak forces because they are weaker than the chemical bonds between molecules or atoms. The starting point for understanding these forces is the four forces of …