Question

At a spot 3,000 feet above sea level you take a sip of water through a straw before you begin a mountain hike. You take another sip when you reach the top at \(10,400 \mathrm{ft}\). At which elevation is it easier to sip the water? Explain.

Short answer

It's easier to sip water at 3,000 feet due to higher atmospheric pressure.

Step-by-step solution

Understanding Atmospheric Pressure

At sea level, atmospheric pressure is highest due to the weight of the air above. As you ascend in elevation, atmospheric pressure decreases because there is less air above you. This difference in pressure affects the ease of sipping water through a straw.

Analyzing Pressure at Starting Elevation

At 3,000 feet above sea level, atmospheric pressure has already decreased from sea level. However, it is still higher than the pressure at 10,400 feet. This translates to relatively higher atmospheric pressure pushing on the liquid in the straw.

Analyzing Pressure at Top Elevation

At 10,400 feet, atmospheric pressure is significantly lower than at 3,000 feet. Since sipping through a straw relies on reducing pressure inside the straw compared to outside, with lower atmospheric pressure, it becomes harder to reduce the pressure further to sip efficiently.

Comparison of Sipping Difficulty

With higher atmospheric pressure (as at 3,000 feet), it is easier for atmospheric pressure to push the liquid up the straw when you sip. Therefore, it is easier to sip water at 3,000 feet than at 10,400 feet.

Key concepts

Elevation

Elevation refers to how high a location is above sea level. This measurement affects numerous environmental parameters, such as temperature and atmospheric pressure. In general, the higher the elevation, the thinner the atmosphere becomes. This means there is less air exerting pressure downward. Understanding the influence of elevation on atmospheric pressure helps to explain many phenomena, including the mechanics of sipping through a straw.

• At sea level, the atmospheric pressure is approximately 1013.25 millibars.
• Each increase of about 1,000 feet results in a decrease of atmospheric pressure by roughly 12 millibars.
• So, at 3,000 feet, there is considerably more air (and therefore more pressure) than at 10,400 feet, where the pressure is much lower.

Studying elevation’s impact reveals why certain activities, like sipping from a straw, become more challenging at greater heights.

Straw Sipping Mechanics

Sipping from a straw involves creating a pressure difference between the inside of the straw and the outside environment. When you suck on a straw, you reduce the air pressure inside it, resulting in atmospheric pressure pushing the liquid upwards. This simple action is guided by principles of physics.

• Creating a vacuum: By sucking the air out, you form a lower pressure zone inside the straw.
• Pressure difference: The higher pressure outside forces the liquid to move into this lower pressure area.
• Effectiveness of sipping increases with greater atmospheric pressure, aiding liquid movement.

When you account for changes in atmospheric conditions with elevation, it becomes clear why straw sipping changes in difficulty at different heights.

Pressure Difference

The concept of pressure difference is central to many natural processes, including drinking through a straw. Pressure difference is what causes fluids to move from areas of higher pressure to areas of lower pressure. In the context of a straw:

• Atmospheric pressure acts as the force that pushes liquid up the straw.
• When you suck the air out of the straw, you create a low-pressure area inside it.
• The remaining atmospheric pressure outside encourages the liquid to rise and fill the void.

This principle is less effective at high elevations because the atmospheric pressure is significantly lower, making it harder to create a sufficient pressure difference. Consequently, sipping water through a straw at 3,000 feet is easier than at 10,400 feet due to the larger available pressure difference, which facilitates the upward movement of liquid.