The phenomenon of recoil is usually explained to students in the context of Newton's third law. Typically, when a projectile is fired, the recoil of the launch mechanism is interpreted as a reaction to the ejection of the smaller projectile. The same phenomenon is also interpreted in the context of the conservation of linear momentum, which is closely related to Newton's third law. Since the actual microscopic causes of recoil differ from one problem to another, some students (and teachers) may not be satisfied with understanding recoil through the principles of conservation of linear momentum and Newton's third law. For these students, the origin of the recoil motion should be presented in more depth.
REFERENCES
1.
2.
See, for example,
W. F.
Weldon
, M. D.
Driga
, and H. H.
Woodson
, “Recoil in electromagnetic railguns
,” IEEE T. Magn.
22
, 1808
(1986
).3.
Other examples include: the rotation of the rotary lawn sprinkler, recoil of a dc motor at its startup, and the recoil of an atom when a photon is spontaneously emitted. For more details on these examples, see the online supplementary material at http://dx.doi.org/10.1119/1.3694068.
© 2012 American Association of Physics Teachers.
2012
American Association of Physics Teachers
AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.