兩題中大推甄試題，不知道怎麼翻比較好，請教一下，感激不盡!!
A rigid body is said to be translating if all lines in the body remain
parallel to their original positions. Therefore, translation implies the
absence of rotation. Consequently, the velocities and accelerations of all
points of the body are equal, so the motion of any one point of the body
determines the motion the entire body. On the other hand, rotation about a
fixed axis is a special case where one line in the body, called the axis of
motion, is fixed in space. Since the body is rigid, the path of each point
(except points on the axis of rotation) is a circle with its center on the
axis of rotation. All points remain a fixed distance from a reference plane
that is perpendicular to the axis of rotation.
In problems of mechanics, we can delineate different classes of situations
concerning equivalence of vectors. First, we have the situations in which
vectors may be positioned anywhere in space without loss or change of meaning
provided that magnitude and direction are kept intact. Under such
circumstances the vectors are called free vectors. On the other hand, there
are situations in which the vectors must be applied at definite points. The
point may be represented as the tail or head of the arrow in the graphical
representation. These vectors are called bound vectors
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