The elastic potential energy stored in the spring is 0.375 J.
The formula for elastic potential energy is:
E = 1/2 * k * x^2
where:
* E is the elastic potential energy in Joules
* k is the spring constant in N/m
* x is the distance the spring is stretched or compressed from its equilibrium position in meters
In this problem, we have:
* k = 3 N/m
* x = 0.5 m (50 cm)
Substituting these values into the formula, we get:
E = 1/2 * 3 * 0.5^2 = 0.375 J
Therefore, the elastic potential energy stored in the spring is 0.375 J.