A spring is attached at one end and stretched by a force $F$ applied to the opposite end. Its extension is $x$ and its elastic potential energy is $E_p$. The spring constant is $k$. The spring follows Hooke’s law. Which relationship is correct for this spring?
- A$E_p \propto F$
- B$E_p \propto x$
- C$E_p \propto k$
- D$E_p \propto x^2$