To develop this problem it will be necessary to apply the concepts related to the frequency of a spring mass system, for which it is necessary that its mathematical function is described as
[tex]f = \frac{1}{2\pi} \sqrt{\frac{k}{m}}[/tex]
Here,
k = Spring constant
m = Mass
Our values are given as,
[tex]m = 35g = 35*10^{-3}kg[/tex]
[tex]f = 1 Hz[/tex]
Rearranging to find the spring constant we have that,
[tex]k = (2\pi f \sqrt{m})^2[/tex]
[tex]k = 4\pi^2 f^2 m[/tex]
[tex]k = (4) (\pi)^2 (1) (35*10^{-3})[/tex]
[tex]k = 1.38N/m[/tex]
Therefore the spring constant is 1.38N/m