Show that for an observer at rest relative to [ i.e. with a
four- velocity
], the particle's three- velocity
can be written as
A particle moves with variable velocity relative to some inertial
frame, under the action of a force
. Show that
where v is the magnitude of . Infer that
if the acceleration is parallel to , while
if the acceleration is perpendicular to .
Suppose the particle moves along the x- axis under a force of magnitude
being at rest at t=0. Show that the time taken to move to the point with
coordinate is
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Peter Dunsby