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ERIC Number: EJ876093
Record Type: Journal
Publication Date: 2010-Jan
Pages: 2
Abstractor: As Provided
Reference Count: 7
ISBN: N/A
ISSN: ISSN-0031-921X
Energy in a String Wave
Ng, Chiu-king
Physics Teacher, v48 n1 p46-47 Jan 2010
When one end of a taut horizontal elastic string is shaken repeatedly up and down, a transverse wave (assume sine waveform) will be produced and travel along it. College students know this type of wave motion well. They know when the wave passes by, each element of the string will perform an oscillating up-down motion, which in mechanics is termed "simple harmonic". They also know elements of the string at the highest and the lowest positions--the crests and the troughs--are momentarily at rest, while those at the centerline (zero displacement) have the greatest speed, as shown in Fig. 1. Irrespective of this, they are less familiar with the energy associated with the wave. They may fail to answer a question such as, "In a traveling string wave, which elements have respectively the greatest kinetic energy (KE) and the greatest potential energy (PE)?" The answer to the former is not difficult; elements at zero position have the fastest speed and hence their KE, being proportional to the square of speed, is the greatest. To the PE, what immediately comes to their mind may be the simple harmonic motion (SHM), in which the PE is the greatest and the KE is zero at the two turning points. It may thus lead them to think elements at crests or troughs have the greatest PE. Unfortunately, this association is wrong. Thinking that the crests or troughs have the greatest PE is a misconception.
American Association of Physics Teachers. One Physics Ellipse, College Park, MD 20740. Tel: 301-209-3300; Fax: 301-209-0845; e-mail: pubs@aapt.org; Web site: http://scitation.aip.org/tpt
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A
Identifiers - Location: Hong Kong