Forces and Motions

Types of Motion. — The motions of bodies may be divided into three classes: (1) translation, (2) rotation, and (3) vibration or oscillation. A body is said to have a motion of translation when it moves on continuously in the same direction. A ball thrown from the hand and an automobile running on a straight road are illustrations of motions of translation. If a body instead of travelling forward turns on fixed axis, it has a motion of rotation. Thus the flywheel of a stationary engine turns continuously around its axis without ever moving forward. Any point on the wheel returns again and again to its original position. This is a motion of rotation. The drive wheels of a locomotive are moving forward and are at the same time rotating. Therefore they have two motions, one of rotation and the other of translation. Some bodies reverse their motions from time to time and return at regular intervals to their original positions. Such bodies are said to have a motion of vibration or oscillation. The pendulum of an ordinary clock swings back and forth at regular intervals, so that the same motion is repeated again and again. The bob of the pendulum has a motion of vibration [2, С. 51].

Summary variants:

· Translation is a motion with the continuous changing of the direction, while rotating means circling and oscillation represents a periodic motion.

· Translation is a continuous forward motion, while rotating means swinging back and forth and oscillation represents a motion with some intervals.

· Translation is a forward motion in a straight line, while rotating means revolving on the axis and oscillation represents reversing motion with some periodicity.

Read the text, translate it and find out what sentences to the text are false.

<== попередня сторінка	\|	наступна сторінка ==>
Figure 16 - Angular displacement	\|	Speed and Velocity

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