Formula: Ca=Vt^2/r
centripetal acceleration(Ca)= ?
tangential speed(Vt)= 2.8m/s
Radius(r)=2m
Substitute: Ca=2.8^2/2
Ca=3.92m/s^2
Well water would prob be your best bet, you could extract the salt first and then use a magnet to seperate the iron filing from the sand
I think 30 as that’s usually average speed