A problem addressed infrequently in beginning physics courses is that of a moving body with changing mass. Elementary texts often have footnotes referring to jet planes and rockets but rarely do they go further. This omission is understandable because calculations with variable mass generally require the tools of calculus. This paper presents a changing mass problem that can be treated on an elementary level, thereby leading to an understanding of the role of changing mass on Newton's second law. It also illustrates Mazur's technique of Peer Instruction, a technique that demands active student participation.

Topics
Newtonian mechanics, Hooke's law, Jet planes, Education
1.
E. Mazur, Peer Instruction — A User's Manual (Prentice-Hall, Upper Saddle River, NJ, 1997).
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© 2009 American Association of Physics Teachers.
2009
American Association of Physics Teachers
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