How to close programs in the Android-x86 emulator?

This may seem like an odd question but I cannot resolve it. I am using the Android-x86 emulator in VirtualBox (https://www.android-x86.org/documentation/virtualbox.html) . I open various apps like Firefox, Chrome, Maps, etc. Normally, I would click the 'x' or go to a menu which said 'exit'. But there is nothing like that. Swiping the app up / down / left / right does nothing. I use "Force Stop" in Settings but that doesn't close the program. In Ubuntu, I can ps aux | grep program_name and then kill the PID. But ps aux does not work in the Android Terminal. How can I close those apps? Can I use the terminal to close programs?