Welcome to the CH forums.
Homework? Goto homework.com.
Physical access is when something can be accessed physically i.e. you can pick up your pc and throw it out of the window, or rip the processor from the motherboard and fit a new one, or disconnect an external drive, etc... etc...
Logical access is when you use software to access information in the processor or external drive. By opening a file using Explorer you have accessed the file logically.
Hope this helps just a little.
Good luck
