Here are some minimal pairs to practice vowels /ɑ:/ and /ʌ/ :
Click on the image to hear the words.
(taken from http://www.shiporsheep.com/page8.html)
And here are some more minimal pairs to practice these vowels:
Minimal Pairs
calm – come
cart – cut
card - cud
tart – tut
cart – cut
card - cud
tart – tut
heart – hut
karting – cutting