At the top of a mountain, the pressure is found to be 0.52 atmospheres. how does this compare to standard atmospheric pressure at sea level?

It is less than(almost half) the atmospheric pressure at sea level.

Explanation:

When we move up high , the pressure decreases with increase in altitude.

The pressure or atmospheric pressure is due to air present.

As we move up, with the altitude the amount of air decreases which cause a decrease in atmospheric pressure.

If the pressure found to be 0.52 atm at the top of mountain it is due to higher altitude.

This is less than the normal or standard atmospheric pressure at sea level which is 1013.25 mbar or 1 atm.

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