Halliday, Resnick & Walker — Relativity: Problem 32

32 An electron of \(\beta = 0.999\,987\) moves along the axis of an evacuated tube that has a length of \(5.00\text{ m}\) as measured by a laboratory observer \(S\) at rest relative to the tube. An observer \(S'\) who is at rest relative to the electron, however, would see this tube moving with speed \(v (= \beta c)\). What length would observer \(S'\) measure for the tube?