Calculating the motion of air cylinder

[Some1WhoNeedsHelp]

Homework Statement

Find the time and velocity of the cylinder

Relevant Equations

ρ=m/V

I am stuck at A, how do you calculate the motion of the air?
I know ρ=m/V but what is the mass of the air, or I got that question wrong?

Thanks

 

[BvU]

I'm stuck at reading your unsharp picture . Doesn't it vaguely say the motion of the air can be neglected ?

https://www.physicsforums.com/threads/homework-help-guidelines-for-students-and-helpers.686781/

$\$

 

[haruspex]

Doesn't it vaguely say the motion of the air can be neglected ?

The opposite… that the motion of the glass can be neglected in comparison to the motion of the air. Even then, we are told to show that, not assume it.

 

[haruspex]

what is the mass of the air

I think you are supposed to treat it as a body of air, at atmospheric pressure, of the same volume as the space to be filled. As such, it is just a mass to be propelled by a constant pressure difference.
What bothers me is the mix of basic and advanced concepts in the one question. Makes it hard to know what degree of sophistication is expected in the answer. Are we expected to treat it as Bernoulli for compressible fluid?
I guess we can rule out a molecular kinetics approach, in which there would be no specific time at which the air as a whole reaches the water. Rather, some molecules would arrive at up to 400m/s, others rather later as they bounce around along the way.

 

[berkeman]

Thread closed for Moderation...

 

[berkeman]

Thread will remain closed.

Homework Statement:: Find the time and velocity of the cylinder
Relevant Equations:: ρ=m/V

I am stuck at A, how do you calculate the motion of the air?
I know ρ=m/V but what is the mass of the air, or I got that question wrong?

@Some1WhoNeedsHelp -- Please post a new thread start with the suggestions that I sent you in a PM. Thank you.