Answer
a. 18 N/m
b. 1.3 Hz
Work Step by Step
a. Use equation 11-6b to relate frequency, mass, and spring constant.
$$f=\frac{1}{2 \pi}\sqrt{\frac{k}{m}}$$
$$k=4 \pi^2f^2m=4 \pi^2(3.0Hz)^2(0.052kg)=18.476 N/m \approx 18 N/m$$
b.
$$f=\frac{1}{2 \pi}\sqrt{\frac{18.476 N/m}{0.28kg }}\approx 1.3 Hz$$