" @hitsusatsu11: I don't think that power levels are linear because if we went by that logic, someone with a power level of 5 or 10 could bust mountains.Yes but while a normal human may have a powerlevel of 4 or 5, they posses no ki control and no way to concentrate their ki into a beam or their physical attacks, but certainly everyone in DBU has some considerable spirit, at least enough to contribute to the Genkidama.
Also Yamucha and Goku with a powerlevel of like 6 were able to punch through cement, knock people through tree's and stuff, tank bullets, lift larger objects then normal folks could and survive fairly long falls.
While roshi was able to destroy the moon, it did seem to take some effort for him to bust the ox king's mountain and his power level was something around 120 or 130? "Well he was rusty on the use of his beam, and just intended to put out the fire with the kamehameha leaving the mountain and castle in tact. He accidentally used to much power and the mountain was destroyed.