Welcome to SolidWorks forums Aaral.
You need to specify the material for simulation. You can make your material and assign some properties to that. And then apply that material to electronic components. If those components are not required for simulation then you may suppress them too.
You might also find this post helpful for your future reference.
you could use a remote mass in this case
or replace their weight with a force
just make sure you recognize the assumptions that are made by these simplifications