4th. Retarded.
4th. Retarded,—when the distances traversed in equal times are successively less and less.
Acceleration or Retardation, may also be equal or unequal, that is uniform or variable.
Friction.
Friction,—arises from the irregularities of the surfaces which act upon one another.
Force.
Force,—any cause which produces, or tends to produce a change in the state of rest, or of motion of a particle of matter.
Measure of force.
Forces are measured by comparison with weights. Thus any forces which will bend a spring into the same positions as weights of 1lb., 2lbs., 3lbs., &c., are called respectively forces of 1lb., 2lbs., 3lbs., &c., &c.
Momentum.