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Physics For Class IX (Science Group)
UNIT 7: PROPERTIES OF MATTER
Numericals
WORKED EXAMPLES
Numerical From Text Book Exercise
Gases and Kinetic theory7. The pressure on 9 cm3 of oxygen gas is doubled at a fixed temperature. What will its volume become?
Solution:
Data:
- Initial pressure = P1 = P1
- Final pressure = P2 = 2P1
- Initial volume = V1 = 9 cm3
- Final Volume = V2 = ?
Working Formula:
P1V1 = P2V2
Calculation:
P1 x (9) = (2P1) x V2
Ans: Hence, Its volume will become 4.5 cm3
8. A container holds 30 m3 of air at a pressure of 150000 Pa. If the volume changed to 10 m3 by decreasing load on the piston. What will the pressure of the gas become? Assume that its temperature remains constant.
Solution:
Data:
- Initial pressure = P1 = 150000 Pa
- Final pressure = P2 = ?
- Initial volume = V1 = 30 m3
- Final Volume = V2 = 10 m3
Working Formula:
P1V1 = P2V2
Calculation:
(150000) x (30) = P2 x (10)
4500000 = P2 x (10)
P2 = 4500000/10 = 450000 pa.
9. Air at atmospheric pressure of 760 mm of Hg is trapped inside a container available with a moveable piston. When the piston is pulled out slowly so that the volume is increased from 100 dm3 to 150 dm3, the temperature remaining constant. What will be the pressure of the air becomes?
Solution:
Data:
- Initial pressure = P1 = 760 mm of Hg
- Final pressure = P2 = ?
- Initial volume = V1 = 100 dm3
- Final Volume = V2 = 150 dm3
Working Formula:
P1V1 = P2V2
Calculation:
(760) x (100) = P2 x (150)
76000 = P2 x (150)
P2 = 76000/150 = 506.67 mm of Hg
Ans: Hence, The pressure of the air will become 506.66 mm of Hg
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