I had unprotected sex, took the plan b but had sex the next day. should i take another plan b or since it did not pass 24 hours, the first one will do?

Not a simple answer: You really should not be depending on Plan B for your birth control. It doesn't always work and it is uncertain whether taking another will improve your protection, but it will definitely increase your chance of having a bad reaction to the medication itself.

It will likely: still cover you but Plan B is only designed to be used when other forms of birth control fail. You need to be responsibily use some form of protection every time you have sexual intercourse if you are not ready for pregnancy.