Answer:
double the force constant
Explanation:
For this exercise we see that the unit mass to the spring executes a simple harmonic motion, the maximum mechanical energy is
Em = ½ k A²
where A is the range of motion
To double the energy we must increase the amplitude or the spring constant
Therefore, to double the total energy we must increase the amplitude by an amount √2
or we can increase the spring constant to double
The correct answer is to double the force constant