Question

The atmospheric pressure decreases as we move upwards from the surface of the earth because:

• A. the density of air increases as we move upwards
• B. the density of air remains the same as we move upwards
• C. the density of air decreases as we move upwards
• D. the weight of air increases as we move upwards

Answer 1

The correct option is C

the density of air decreases as we move upwards

The explanation for the correct answer: Option C

1. As we move upwards from the surface of the earth the earth's gravity decreases and hence the density of the air decreases.
2. The atmospheric pressure (pressure exerted by the gases present in the atmosphere) also decreases.
3. Thus, as we move upwards from the earth's surface the atmospheric pressure decreases.

The explanation for the incorrect answer: Option A

1. As we upward in the atmosphere the density of the air decreases
2. The gravitational pull of the earth decreases as we move up.
3. Therefore density of the air decreases as we move upwards from the surface of the earth.

The explanation for the incorrect answer: Option B

1. The density of air does not remain the same as we upward but decreases.
2. Because the gravitational pull on the air molecules decreases as we move upwards
3. Hence the density of the air does not remain the same as we move upwards.

The explanation for the incorrect answer: Option D

1. The weight is the force experienced by an object towards the center of the earth.
2. The weight of air decreases as we move upwards because it causes a reduction/decrease in the gravitational pull experienced by the earth's surface.
3. Hence the weight of air decreases as we move upwards

Conclusion:

Hence option C is the correct option.