- A standard pressure of 1013.25 millibars is also known as one atmosphere (1 ATM).
(a) Look at Fig. 1.10 and determine at approximately what levels you would record a pressure of 0.5 ATM and 0.1 ATM.
(b) The surface air pressure on the planet Mars is about 0.007 ATM. If you were standing on Mars, the surface air pressure would be equivalent to a pressure observed at approximately what altitude in Earth’s atmosphere?
- If you were suddenly placed at an altitude of 100 km (62 mi) above Earth, would you expect your stomach to expand or contract? Explain.
The Correct Answer and Explanation is :
Answer:
1(a). Determine levels for pressures of 0.5 ATM and 0.1 ATM
From standard atmospheric pressure (1 ATM = 1013.25 millibars), the relationship between altitude and pressure can be approximated using the barometric formula. Based on Figure 1.10, which typically depicts a logarithmic relationship between altitude and pressure:
- At 0.5 ATM (506.63 millibars): This pressure corresponds to approximately 5.5 km (18,000 feet) above Earth’s surface.
- At 0.1 ATM (101.33 millibars): This pressure is observed at around 16 km (52,500 feet) above Earth’s surface.
1(b). Equivalent altitude on Earth for 0.007 ATM (Mars’ surface pressure)
Mars’ surface pressure is 0.007 ATM (7 millibars). On Earth, such a pressure corresponds to an altitude of approximately 50 km (164,000 feet) above sea level. This altitude lies in the mesosphere, far above the highest level at which commercial aircraft operate and is well into the thin, almost vacuum-like regions of Earth’s atmosphere.
2. Stomach expansion or contraction at 100 km altitude
If you were suddenly placed at an altitude of 100 km (62 miles) above Earth, your stomach would expand dramatically. Here’s why:
At 100 km altitude, the pressure is nearly a vacuum (~0.00003 ATM). At such low pressures, external atmospheric pressure is almost nonexistent. However, the gas inside your stomach remains at a higher pressure, close to 1 ATM (if you recently ate or drank, the pressure could be even higher). This imbalance between internal and external pressure causes the trapped gas in your stomach to expand significantly.
This expansion is explained by Boyle’s Law, which states that the volume of a gas increases as the external pressure decreases, provided the temperature remains constant. The low external pressure at 100 km means any gas within your stomach, lungs, or tissues would expand uncontrollably, causing severe harm. Without a pressurized suit, the rapid expansion could lead to internal ruptures or decompression sickness.
This is why space suits are crucial in maintaining a pressurized environment to protect astronauts from such effects.