Resnick/Halliday/Walker is a great book for undergraduates for self learning 

What's the first physics textbook for undergraduate self-learner？
I already have my home WiFi but I was wondering if it would be possible to create a temporary pass for when the guests come to visit? I would like to give them a password to the network but I would want it to die off after say 30 minutes. Is something like this possible? 

PS I can't modify the firmware on the router.
