Not a skater, but, I am a "nerd". It's because you push OFF of the skateboard. It's hard to explain, but go to youtube, and watch how their feet are angled, and which way the board goes. It will make better sense. Easier to show than tell. Never seen anyone jump off a skateboard and NOT have it go the other way, if you do, Good Job, because I hang out with a lot of really good skaters!
friction
no they tell someone.
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The prepositional phrase is "off of his skateboard" but the compound preposition "off of" is poor English. You need only use the word OFF as a preposition instead of an adverb and say he "fell off his skateboard" which means exactly the same thing.
-- subtract the percent off from 100 -- divide the sale price by the answer -- multiply that answer by 100, and you have the original price
Yeah, It is.
no
A plan b
its called "balance"
...he exerts against the ground
The preposition is of.The prepositional phrase is: of his skateboard.