#### Answer

(a) The force exerted on the flat end of each cylinder is $2.9\times 10^4~N$
(b) 30 football players would need to hang from the lower cylinder to pull the two cylinders apart.

#### Work Step by Step

(a) The pressure difference between the inside of the cylinders and the outside of the cylinders is $1~atm$. We can find the force exerted on the flat end of each cylinder.
$F = \Delta P~A$
$F = \Delta P~\pi~r^2$
$F = (1.013\times 10^5~N/m^2)(\pi)(0.30~m)^2$
$F = 2.9\times 10^4~N$
The force exerted on the flat end of each cylinder is $2.9\times 10^4~N$
(b) We can find the weight of one football player.
$weight = (100~kg)(9.80~m/s^2) = 980~N$
We can find the number $n$ of football players.
$n\times ~weight = 2.9\times 10^4~N$
$n = \frac{2.9\times 10^4~N}{weight}$
$n = \frac{2.9\times 10^4~N}{980~N}$
$n = 30~players$
30 football players would need to hang from the lower cylinder to pull the two cylinders apart.