Question

Consider the following apparatus: a test tube covered with a nonpermeable elastic membrane inside a container that is closed with a cork. A syringe goes through the cork. a. As you push down on the syringe, how does the membrane covering the test tube change? b. You stop pushing the syringe but continue to hold it down. In a few seconds, what happens to the membrane?

Short answer

a. As you push down on the syringe, the pressure inside the container increases, causing the elastic membrane to stretch and respond to the applied pressure. b. When you stop pushing the syringe but hold it down, the membrane tries to achieve equilibrium as the air pressure equalizes throughout the container. The membrane may show slight changes, such as relaxation or tension, depending on its elasticity, and will likely stay in place as long as the pressure is still higher on the outside than inside the test tube.

Step-by-step solution

Visualize the setup

Imagine a container with a cork, and a syringe going through the cork. Inside the container, there is a test tube covered by a nonpermeable elastic membrane.

Explain the effect of pushing down on the syringe

As you push down on the syringe, the pressure from air being compressed in the container increases. This increased pressure causes the elastic membrane to stretch and respond to the applied pressure. Part b:

Visualize the changed situation

You stop pushing the syringe but continue to hold it down. The air pressure remains high in the container as the air is trapped inside.

Explain the effect on the membrane

In a few seconds, the membrane would try to achieve equilibrium as the air pressure tries to equalize throughout the container. The membrane may show some slight changes, such as slight relaxation or tension, depending on how elastic and flexible it is. The membrane will likely stay in place as long as the pressure is still higher on the outside than inside the test tube.