The gravitational interaction between a relatively massive body and a field of much less massive bodies through which the massive body travels. As a result, the moving body loses momentum and kinetic
energy. An example of dynamical friction is the sinking of massive stars to the center of a star cluster, a process called mass segregation. Dynamical friction plays an important role in stellar dynamics. It was first quantified by Chandrasekhar (1943).
A method for deriving the distance to a binary star. The angular diameter of the orbit of the stars around each other and their apparent brightness are observed. By applying Kepler's laws and the mass
-luminosity relation, the distance of the binary star can be calculated.
The absolute value of the ratio between the linear strain changes, perpendicular to and in the direction of a given uniaxial stress change, respectively, under dynamic loading conditions
Dynamic pressure is a measure of the kineticenergy per unit volume of a fluid. For instance, the solar wind dynamicpressure or ram pressure for a purely proton plasma is equal tomp n V2 wheremp is the proton mass, n the proton number density,and V the solar wind speed.