Short Answer Questions – Atmospheric Pressure
1. What do you understand by the term atmospheric pressure?
Atmospheric pressure is the pressure exerted by the weight of air present in the atmosphere on the surface of the earth.
2. Why don't we feel uneasy under atmospheric pressure?
Because the blood pressure inside our body balances the atmospheric pressure acting from outside.
3. Describe an experiment to demonstrate that air exerts pressure.
Take a tin can filled with a little water and heat it. After steam fills the can, close it tightly and cool it. The can collapses showing air pressure from outside.
4. Explain the following:
(i) A balloon collapses when air is removed from it.
(ii) Water does not run out of a dropper unless its rubber bulb is pressed.
(iii) Two holes are made in a completely filled sealed tin can to take out oil from it.
(i) A balloon collapses when air is removed from it.
(ii) Water does not run out of a dropper unless its rubber bulb is pressed.
(iii) Two holes are made in a completely filled sealed tin can to take out oil from it.
(i) Due to atmospheric pressure acting from outside.
(ii) Because the pressure inside and outside remains equal until pressed.
(iii) One hole lets air in, helping the oil flow out smoothly.
(ii) Because the pressure inside and outside remains equal until pressed.
(iii) One hole lets air in, helping the oil flow out smoothly.
5. Why does the liquid rise in a syringe when its piston is pulled up?
Pulling the piston creates low pressure inside, so atmospheric pressure pushes the liquid up into the syringe.
6. How is water drawn up from a well by a water pump?
The pump creates a low-pressure region, and atmospheric pressure pushes water up the pipe into the pump.
7. How is the height of mercury column in a barometer a measure of atmospheric pressure?
The height of the mercury column balances the atmospheric pressure, indicating its value in cm of mercury (Hg).
8. Labelled diagram of a simple barometer showing 76 cm of Hg.
A vertical glass tube filled with mercury, inverted in a mercury trough. The column height is 76 cm showing atmospheric pressure.
9. Why is barometric height used as a unit of atmospheric pressure?
Because the height of mercury directly reflects atmospheric pressure and is easy to measure.
10. How to show vacuum above mercury in a barometer? Name the vacuum.
No mercury is present at the top of the tube; this empty space is called Torricellian vacuum.
11. Two reasons for using mercury as barometric liquid.
Mercury is dense and does not evaporate easily, allowing a shorter column and more accuracy.
12. Two reasons why water is not suitable as barometric liquid.
Water has low density, requiring a very long tube, and it evaporates quickly.
13. Two advantages of an aneroid barometer over a simple barometer.
It is portable and does not contain liquid mercury.
14. How does atmospheric pressure change with altitude? Draw a graph.
Atmospheric pressure decreases with increase in altitude. [Graph: Downward sloping curve]
15. State two factors which affect the atmospheric pressure as we go up.
Air density and temperature both affect atmospheric pressure at higher altitudes.
16. Why does a fountain pen leak at a high altitude?
At high altitudes, atmospheric pressure decreases but pressure inside the pen remains high, pushing ink out.
17. Why does our nose start bleeding on high mountains?
Low pressure at high altitudes causes blood vessels to burst due to internal body pressure, leading to nose bleeding.
