1. Find the Spring Constant (k)

* We know the frequency (f) of the SHM and the mass (m). The relationship between frequency, mass, and spring constant is:

* f = (1 / 2π) * √(k/m)

* Solve for k:

* k = (2πf)² * m

* k = (2π * 0.70 Hz)² * 0.050 kg

* k ≈ 1.94 N/m

2. Calculate the Extension (x)

* The extension is given as 15 cm, which is 0.15 m.

3. Calculate the Work Done

* The work done in stretching the spring is equal to the potential energy stored in the spring. The potential energy (PE) in a spring is given by:

* PE = (1/2) * k * x²

* PE = (1/2) * 1.94 N/m * (0.15 m)²

* PE ≈ 0.0218 J

Therefore, the work done in stretching the spring is approximately 0.0218 Joules, and this is also the amount of energy stored in the spring.