We saw Roshi blow up the moon during the 21st Budokai. Really doesn't mean much. Early Dragonball was loaded with inconsistencies, toonforcing and crossovers, like with appearances by Arale. Anyway, that Boulder feat by Krillin and Goku. That thing is solid granite and is estimated around 20tons. That's no small feat for 6yr old kids. Also, Roshi made them do that just as Test before he'd train them (he honestly didn't want to and used the boulder as an excuse, but it backfired). Now, this is 22d Budokai Krillin, after years of training. Think he's like 10-11yrs old now and was giving Goku a decent run.
Ok first off. krillen is not a 6 year old and neither is Son Goku. Krillin at this time is roughly 13 year old and Goku is roughly 11 years old. Also that Boulders real life counter part is 350 tons, not 20 tons. We actually did an estimate of it on Kazenshuu forum. By the way a tank is 40 tons.
For comparison, this real life boulder weight 340 tons:
Question: Where did you get that the second boulder was 340 tons? I mean, could I see this calculation?