# Chapter 22 - Problems - Page 865: 57

(a) $f_2 \gt f_1$ (b) $f_2-f_1 = 1200~Hz$

#### Work Step by Step

(a) Since the speeder is approaching the police car, the speeder will detect a higher frequency $f_2$ than the frequency $f_1$ that the waves were emitted. That is, $f_2 \gt f_1$ (b) We can find $f_2-f_1$: $\frac{f_2-f_1}{f_1} = \frac{v}{c}$ $f_2-f_1 = \frac{v}{c}~f_1$ $f_2-f_1 = \left(\frac{48.0~m/s}{3.0\times 10^8~m/s}\right)~(7.50\times 10^9~Hz)$ $f_2-f_1 = 1200~Hz$

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