$($b$)$ A conical converging pipe converges uniformly from $0\mathrm{.}4$ m diameter to $0\mathrm{.}2$ m diameter over a length of $2$ m $.$ Find the local and convective acceleration at the middle of the diffuser for $($a$)$ constant flow rate of $50\frac{l}{s}$ and $($b$)$ flow rate varies uniformly from $50\frac{l}{s}$ to $100\frac{l}{s}$ in $5$ sec and the time of interest is $2$ sec $.$ Velocity at any cross section is uniform.