Powershell remote get-process works, start-process doesn't

I'm new to Powershell, so forgive me if this is a basic question. I've enabled psremoting, but for some reason, while

invoke-command -computername MyComputer {get-process}

works,

invoke-command -computername MyComputer {start-process "c:\windows\system32\calc.exe"}

doesn't. I don't get an error message. Rather than the calculator app starting, nothing happens and I get no feedback. Am I missing something?