# Columbia Encyclopedia

98 results found

## velocity

(Encyclopedia)velocity, change in displacement with respect to time. Displacement is the vector counterpart of distance, having both magnitude and direction. Velocity is therefore also a vector quantity. The magnit...

## escape velocity

(Encyclopedia)escape velocity, the velocity a body must be given in order to escape the gravitational hold of some other larger body, e.g., the earth, moon, or sun. A body given less than the escape velocity will f...

## acceleration

(Encyclopedia)acceleration, change in the velocity of a body with respect to time. Since velocity is a vector quantity, involving both magnitude and direction, acceleration is also a vector. In order to produce an ...

## viscosity

(Encyclopedia)viscosity, resistance of a fluid to flow. This resistance acts against the motion of any solid object through the fluid and also against motion of the fluid itself past stationary obstacles. Viscosity...

(Encyclopedia)radial velocity, in astronomy, the speed with which a star moves toward or away from the sun. It is determined from the red or blue shift in the star's spectrum. ...

## speed

(Encyclopedia)speed, change in distance with respect to time. Speed is a scalar rather than a vector quantity; i.e., the speed of a body tells one how fast the body is moving but not the direction of the motion. If...

## Reynolds number

(Encyclopedia)Reynolds number [for Osborne Reynolds], dimensionless quantity associated with the smoothness of flow of a fluid. It is an important quantity used in aerodynamics and hydraulics. At low velocities flu...

## mass spectrograph

(Encyclopedia)mass spectrograph, device used to separate electrically charged particles according to their masses; a form of the instrument known as a mass spectrometer is often used to measure the masses of isotop...

## motion

(Encyclopedia)motion, the change of position of one body with respect to another. The rate of change is the speed of the body. If the direction of motion is also given, then the velocity of the body is determined; ...

## momentum

(Encyclopedia)momentum mōmĕnˈtəm [key], in mechanics, the quantity of motion of a body, specifically the product of the mass of the body and its velocity. Momentum is a vector quantity; i.e., it has both a magn...