@Rouben Rostamian  Thank you so much, it solves my problem!

@nm Yes, I'm using a different example because I don't want to make it complicated and I think the principle is the same. Although I did make it work and thank you for the help. 

@nm Thank you for your help and it helps a lot. However, in my writing, I did mean h(y) not h(x). This is coming from my homework regarding the mass-spring system with a rubber band. 

This is a website I found which is exactly what I am doing.

https://demonstrations.wolfram.com/MassWithASpringAndARubberBand/