Cost: was free. I believe it is still free.
Pros: Simple physics is a fun game that allows students to learn more about physics. It combines things like tree houses to create on your own and make it strong enough to support "4 people." Students may use this to help them learn more about basic forces. It also implies money so students may try and learn balance between good equipment and costs.
Cons: It can be very difficult and frustrating to obtain three stars. The cost factor makes it much harder because keeping it strong enough and least amount of cost is easier said than done. This may demoralize students but if they can get past that it will be very useful to help with physics.
How to use this in class?
I would use this as a free time app. If they were done with a test earlier than most they would be able to use this app to have fun and learn more about physics.