Answer
a. 0.14 N/m
b. 2.8 Hz
Work Step by Step
a. Use equation 11-6b to relate frequency, mass, and spring constant.
$$f=\frac{1}{2 \pi}\sqrt{\frac{k}{m}}$$
$$k=4 \pi^2f^2m=4 \pi^2(4.0Hz)^2(2.2 \times 10^{-4}kg)=0.1390 N/m \approx 0.14 N/m$$
b.
$$f=\frac{1}{2 \pi}\sqrt{\frac{0.1390 N/m}{4.4 \times 10^{-4}kg }}\approx 2.8 Hz$$