Mrs. Johnson's kid is trying to drink with a straw that runs through an airtight cork in the top of a bottle of water. Please explain to her kid why he won't get any water.
Mrs. Johnson's kid won't get any water because of air pressure. Let's understand why the water won't come out using some basic principles of physics.
When you use a straw to drink, you create a partial vacuum inside your mouth by sucking the air out. This reduced air pressure inside the straw creates suction, which pulls the liquid (in this case, water) up the straw and into your mouth.
In the case of a bottle of water with an airtight cork and a straw, there is a sealed chamber of air above the water level. When you try to create suction by sucking on the straw, the air pressure inside the thin straw decreases. However, the air pressure inside the sealed chamber remains relatively constant, since the cork prevents any air from entering or leaving.
Here's where things get interesting. According to the principles of fluid dynamics, liquids always seek to equalize pressure. Since there is a lower pressure inside the straw, and a higher pressure in the sealed chamber above the water level, the water should naturally flow from the higher-pressure region to the lower-pressure region, i.e., from the sealed chamber down into the straw.
However, there's an important factor to consider - the water needs to displace something in order to flow downward. In this case, it needs to displace the air inside the sealed chamber above the water level. But since the cork is airtight, the water is unable to displace the air, which means it can't flow down into the straw.
In summary, the reason why Mrs. Johnson's kid won't get any water when trying to drink through the straw inserted in the airtight cork is because the air pressure inside the sealed chamber remains constant, and the water is unable to displace the air to flow into the straw.