An impetus is the force behind something, whether it's a boulder rolling down a hill or a person making a decision.

Transcription

1 Noun PETere An impetus is the force behind something, whether it's a boulder rolling down a hill or a person making a decision. Very little would get done if there were no such thing as an impetus: an impetus is some kind of force that gets something or somebody moving. If you push a car that's out of gas, you're the impetus that's getting it moving. An impetus doesn't have to be physical. Advertisers hope their commercials will be an impetus to buy the product. DEFINITIONS AND USAGE EXAMPLES That which drives one; momentum o The tragic accident at the crossroads was the impetus for a meeting on traffic safety. Syn: stimulus PRONUNCIATION Directions: Discuss the meaning of the word with your \ ˈim-pə-təs \ students, with special emphasis on any variations or nuances of the word specific to your discipline. Consider taking it a step further by using one or all of the following ideas as you involve students with the new vocabulary. Remember to preview all content you intend to share with students. Not all items on the lists provided below are appropriate for all classes or age levels.

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3 Mary-Frances Winters is president and founder of The Winters Group, a 31-year-old organization development and diversity-consulting firm, specializing in research, strategic planning, training, and public speaking with an emphasis in ethnic and multicultural issues. Prior to founding The Winters Group in 1984, she was affirmative action officer and senior market analyst at Eastman Kodak Company, where she worked for 11 years. Among her many awards and distinctions, she was named a Diversity Pioneer by Profiles in Diversity Journal in August 2007.

4 CHAPTER TWO: CONCEPTS OF FORCE IN HISTORY 2.1 Aristotelian Force It was Aristotle who first developed a systematic set of ideas about the physical world, which is often referred to as Aristotelian physics. Related to his concept of force is his classification of motion as natural, voluntary, and forced (Jammer, 1957). In the natural motion category, Aristotle believed that objects intrinsically either have a natural tendency to fall down to the earth, which he called gravity, or a natural tendency to rise into the sky, which he called levity. He thought that heavy bodies fall faster because the falling speed is in proportion to the physis (nature) or weight of the objects. The earth and the sky are natural places objects would move to according to their internal natural tendencies. Voluntary motion refers to motion of living organisms such as animals and humans, who are agents able to exert force to make other inanimate things move. Nonliving objects are obstacles that stop or guide motion, but they do not exert forces. In the forced motion category, an object moves because of the moving force applied to it by an agent. The object continues to move after the agent is no longer in contact with it because force is still transmitted to the object through a medium such as air (which is called the antiperistasis theory). Motion in a vacuum is thus not possible. A force does not move an object unless it overcomes the object's inertia, an intrinsic resistance of the object. A constant force applied to an object produces a constant speed which is also inversely proportional to the inertia of the object. In the absence of force, an object would stop immediately. So, forced motion is made consistent to the other two types of motion by Aristotle through his notion of antiperistasis and his theory of entelechy or agency (Leclerc, 1972). In sum, for Aristotle, no motion is possible without force acting on the moving object, or in other words, motion and force are inseparable and a moving object is always an effect of some kind of entelechy, either visible or invisible. 2.2 Impetus Theory In his mechanics, Aristotle confined himself only to the concept of force as the agency involved in motion and ignored the Platonic concept of dynamis or force as inherent in matter (Jammer, 1957). It was upon questioning this idea that Philoponus of Alexandria in the Middle Ages developed a new concept of force. Philoponous argued that when an object is thrown in the air, a force is imparted to the object. This force is responsible for the motion after the hand is no longer in contact with the object. Further, this force is prone to dissipation. Philoponus's idea was then developed by Jean Buridan and Nicole Oresme into the so-called Impetus Theory. In its complete form, the Impetus Theory states: 1) impetus is a kind of (invisible) power, existing in the physical world, which is able to move objects in the same direction as the impetus itself; 2) it can be imparted to an object from another object; 3) depending on the amount of impetus imparted to an object, the object moves correspondingly to that amount; 4) impetus can be dissipated or weakened

5 by the resistance in the medium; 5) because impetus can be either rectilinear or curvilinear, the motions produced by the impetus can also be straight or curved (as the motion in celestial spheres).

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