how to crack rar password on mac

well,many softwares can do this:

How to Open Password Protected RAR Files

Crack RAR passwords with Rar Pass Finder

You will need to get the password from somewhere, either by asking whoever created it, checking the website that had the link you downloaded it from or by using a password cracking application. There are cracking tools for RAR files on the net. Trial version generally work for passwords that are 3 characters or less. The fastest and best tools will cost you hundreds of dollars, so you need to ask yourself if it is worth it in both $$$ and time. Unless you have a VERY powerful computer, cracking the password could take an extremely long time.

 Use any of them here
http://www.google.com.au/search?hl=en&client=opera&hs=bqm&rls=en&q=free+winrar+password+recovery&aq=f&aqi=&aql=&oq=&gs_rfai=

The problem with your situation is, depending on how complex the password is, it going to take awhile to crack the password. What even worse is, most of these software require you to buy to unlock full potential.