posted by jean .
A rod of length 30.0 cm has linear density(mass-per-length) given by
[lambda]= 50.0g/m + 20.0x g/(m^2)
where x is the distance from one end, measured in meters.(a) What is the mass of the rod? (b) How far from the x=0 end is its center of mass?
never mind. i got it.