Chapter 26, Problem 7P

To determine

The lifetime of a ${\sum }^{+}$ particle in the reference frame of a laboratory observer, given that the proper life-time of a ${\sum }^{+}$ particle is $0.80\times {10}^{-10}\text{s}$ and it movesat a speed of $2.4\times {10}^8\text{m/s}$ with respect to the observer.