The usual suggestion for the longitudinally propagating momentum carried by a transverse wave on a string is shown to lead to paradoxes. Numerical simulations provide clues for resolving these paradoxes. The usual formula for wave momentum should be changed by a factor of 2 and the involvement of the cogenerated longitudinal waves is shown to be of crucial importance.
Fundamental solitary waves in a cubic-quintic nonlinear medium are investigated both numerically and variationally. An equivalent particle model is used to understand the behaviour of the numerical solutions, and while a super-Gaussian trial function is found to have only a limited range of applicability in the variational analysis, a super-sech trial function is found to match the numerical solutions well for all input powers. Various limits are also investigated.' Present address: Student Support Services,
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