# Equation of flow rate

1. Apr 12, 2016

### foo9008

1. The problem statement, all variables and given/known data
the equation of flow aret given is [(pi)((r_o)^4 ) / 8μ ] [-d/ds (ρ +yz ) ] , but the ans that i got is - [(pi)((r_o)^4 ) / 8μ ] [-d/ds (ρ +yz ) ] , what's wrong with my working ?

2. Relevant equations

3. The attempt at a solution

2. Apr 12, 2016

### BvU

Try the simpler $$\int_0^{r_0} (r_0^2 -r^2)\, r dr$$to avoid things like the $r_0^3$ (?) in your first step

3. Apr 12, 2016

### foo9008

thanks , i got the ans already