Answer :
To solve this problem we will apply Hooke's law. Which says that the force on a spring is equivalent to the product between the elastic constant and the displacement of the spring.
[tex]F = k x[/tex]
Here,
k = Spring constant
x = Displacement
Rearranging to find the spring constant,
[tex]k = \frac{F}{x}[/tex]
Spring compresses it to 29 cm so
[tex]x = 39- 29 = 10 cm[/tex]
[tex]k = \frac{mg}{x} \rightarrow[/tex] The force in this case is equivalent to the weight of the spring
[tex]k = \frac{2.2 * 9.8}{10 * 10 ^ {-2}}[/tex]
[tex]k = 215.6N/m[/tex]
Therefore the spring constant is 215.6N/m