im in first year engineering, i wanted to change my physics lab section to another time, and i thought i could do this by dropping the course and adding it in again, but after dropping it and trying to add the course in again mosaic tells me the deadline already passed. when i check grades section my physics mark is also a "W". HEEELP WHAT DO I DO NOW

Contact an academic advisor ASAP. Don't expect anything to happen before Monday. You should probably go see them in person then, though.

Hasn't the deadline already passed for changing sections online as well?

Hey,

You can go to JHE-A214 on Monday, they have drop in hours from 1:30 pm to 4:00 pm just explain your situation to them. I am pretty sure they'll solve the issue for you without any problem. You'll just have to wait until Monday. Also, you can call them up early morning on Monday and explain your situation [905-525-9140 Ext: 24646]. I hope that helps... Good Luck!
http://www.eng.mcmaster.ca/current/advising.html

I'm sure you will be fine, last term I got a class added a week after the deadline.

And just so you know for next time, to switch lab sections, you go under Enroll -> Swap. Then select to swap the course with itself. When you swap a course with itself it prompts you to reselect core/lab/tutorial sections so that you can keep the same lecture and change lab #, or vice versa or just change all sections.