NCERT/CBSE PHYSICS CLASS 11 textbook
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Solutions/Answers to NCERT/CBSE PHYSICS Class 11(Class XI)textbook
Exercise and Additional exercise
CHAPTER THIRTEEN
Kinetic Theory
EXERCISES
(For simplicity in numerical calculations, take g = 10 m s-2)
13.11 A metre long narrow bore held horizontally (and closed at one end)
contains a 76 cm long mercury thread, which traps a 15 cm column of air.
What happens if the tube is held vertically with the open end at the
bottom ?
13.11
When the tube is held horizontally, length of mercury thread = 76 cm
length of air = 15 cm.
Blank space at the open end = 100 − 76 − 15 = 9cm
Pressure of air closed in the tube is atmospheric pressure.
P1 = 76cm, V1 = 15cm3
When tube is held vertically.
Let the total length of air be = 2.15 + 9 + h and length of
mercury column = 76 − h
P2
Pressure of air = 76 − ( 76 − h ) = h cm of Hg
P2
Pressure of air = 76 − ( 76 − h ) = h cm of Hg
P1 V1 = P2 V2
76 ×15 = h × ( 24 − h )
h = 23.8,
When tube is held vertically
Let the tube length of air be = 2.15 + a + h
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47.8 cm
NCERT/CBSE PHYSICS CLASS 11 textbook
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Contact for Online Tutoring in Physics, Math, Chemistry, English
and length of mercury column = 76 − h
P2
Pressure of air = 76 − ( 76 − h ) = h cm of Hg
V2 = ( 29 + h ) cm3
as temperature is constant
P1 V1 = P2 V2
76 × 15 = h × ( 24 + h )
h = 23.8cm,
−17.8 cm.
So h = 23.8 cm. ≈ 24 cm
Length of mercury column = 76 − h = 76 − 24 = 52cm .
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