Use FindRoot solution as number in function

Question

I would like to save a number that I gain with FindRoot so that I can use it in another function. I tried:

alph := FindRoot[BesselJ[0, x], {x, 0, 2}]
f[x_] := alph*x
Plot[f[x], {x, 0, 10}]

This does not work because alph is not a number but an expression {x -> 2.40483}. So how do I do this correctly?