Answer:
U = 12 J.
Step-by-step explanation:
The potential energy in a spring is given by the following formula
![U = (1)/(2)kx^2](https://img.qammunity.org/2021/formulas/physics/high-school/f17pme8d2z2dheyc2ir4phy92tomrnjy0k.png)
where k is the spring force constant and x is the displacement from the equilibrium.
If U = 3 J when x = 0.05 m, then k is
![3 = (1)/(2)k(0.05)^2\\k = 2400~N/m](https://img.qammunity.org/2021/formulas/physics/college/8mes07bj2r84a1vded0b2bavp8obxybxjl.png)
Using this constant, we can calculate the potential energy at x = 0.10 m:
![U = (1)/(2)(2400)(0.1)^2 = 12 ~J](https://img.qammunity.org/2021/formulas/physics/college/8fa2qnsz21hlrnbad4r4pq82idasfwkdes.png)