Calculating Pressure and Steam Jet Velocity in a Boiling Pot

[tweety1234]

Homework Statement

A large pot of water is boiling on the stove. The pot has a heavy, close tting lid
which has a small hole to allow steam to escape, so that the lid does not lift up
from the pot. However, if too much steam is produced to escape through the hole,
the lid will lift to release the excess steam. The lid weighs 2 kg, and is 40 cm in
diameter. The hole for the steam to escape is 3 mm in diameter.

(a) Calculate the pressure that the steam in the pot would need to reach in order
to lift the lid.

(b) The steam exiting the hole forms a small jet as shown in Figure 8. Ignoring
viscosity eects and any small changes in height or density, show that the
maximum rate at which steam could escape from the hole before the excess
pressure lifts the lid is about 0.1 g s^{-1}
.I am not sure what equation to even use? Any help appreciated.

Should I be using Bernoulli's equation for part 'a'?

 

[gneill]

Part (a) asks what pressure is required to lift the lid. You've got the lid weight and its surface area (via its diameter). Do the obvious...

Part (b) may be where Bernoulli comes in. You'll want to look up the density of steam at normal atmospheric pressure.