Chapter 12: Q11P (page 518)
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Chapter 12: Q11P (page 518)
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(a) Equation 12.40 defines proper velocity in terms of ordinary velocity. Invert that equation to get the formula for u in terms of .
(b) What is the relation between proper velocity and rapidity (Eq. 12.34)? Assume the velocity is along the x direction, and find as a function of .
particle’s kinetic energy is ntimes its rest energy, what is its speed?
An ideal magnetic dipole moment m is located at the origin of an inertial system that moves with speed v in the x direction with respect to inertial system S. In the vector potential is
(Eq. 5.85), and the scalar potential is zero.
(a) Find the scalar potential V in S.
(b) In the nonrelativistic limit, show that the scalar potential in S is that of an ideal electric dipole of magnitude
located at .

The parallel between rotations and Lorentz transformations is even more striking if we introduce the rapidity:
(12.34)
(a) Express the Lorentz transformation matrix(Eq. 12.24) in terms of, and compare it to the rotation matrix (Eq. 1.29).
In some respects, rapidity is a more natural way to describe motion than velocity. For one thing, it ranges fromrole="math" localid="1654511220255" to , instead of -c to +c. More significantly, rapidities add, whereas velocities do not.
(b) Express the Einstein velocity addition law in terms of rapidity.
(a) Event happens at point ( role="math" localid="1658241385743" ) and at time given by ; event occurs at role="math" localid="1658241462040" and, both in system .
(i) What is the invariant interval between and ?
(ii) Is there an inertial system in which they occur simultaneously? If so, find its velocity (magnitude and direction) relative to .
(iii) Is there an inertial system in which they occur at the same point? If so, find its velocity relative to .
(b) Repeat part (a) for , ; and , .
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