Why might your eardrums "pop" when you quickly change altitude?
It is due to the change in air pressure around your ears, your ears pop to release the air pressure within.
Why does juice rise up a straw when you drink?
The straw is less dense than the juice inside of the box that is why it floats.
Why does a juice box collapse inward when you drink from it?
The air is being sucked out of the box.
What are two different ways to express the atmospheric pressure at sea level?
Millibars and you could use a barometer.
Why is water pumped into a submarine?
As you blow air into the submarine this will force the water out of the hole in to the ocean.
What happens when the weight of an object is greater than the buoyant force?
It would not float it would sink.