8/18/2019 Physics Topical Examination - Pressure - Copy
1/2
Physics Topical Examination
Topic: Pressure, Atmospheric PressureQuestions:10, Marks:
10X5=50 Time: 2Hrs
1. A cube floating on mercury has 1/4 of its volume submerged.
If enough water is added to
cover the cube, what fraction of its volume will remain immersed
in mercury? (Relative
density of mercury = 13.6)
2. Calculate the depth of water at which a bubble of air would
just float.
= 1000 − and = 1.29 −.
ℎ = 105
3. Two identical cylindrical vessels with their
bases at the same level contain a liquid of
density up to
height hl and h2 , respectively.
Find the work done by gravity in equalising thelevels when the two
vessels are connected. (Area of the base of each cylinder is
A.)
4. A ship with cargo sinks by x when she goes
into a river from the sea. She discharges
cargo and proceeding again to sea, she rises by z. If the sides
of the ship be assumed to be
vertical to the surface of the water, show that relative density
of sea water is
−+ ,
assuming relative density of river water to be 1
5. A beaker containing water is placed on the pan of a balance
which shows a reading of200 g. A lump of sugar weighing 75 g and of
volume 30 cc is now suspended inside thewater from an external
support without touching any part of the beaker, (a) What will be
thereading just when the lump of sugar is immersed? How will the
reading change as timepasses? (b) What will be the initial reading
if the lump is simply dropped gently into thebeaker and how will
the reading change?
6. A beaker filled with water up to the brim contains a piece of
ice floating in the water. Willwater spill as, ice melts?
7. A man in a boat scoops out a stone from the bottom of a lake
and puts it in his boat. Will
the level of water in the lake rise or fall?
8. An ideal gas is trapped between a mercury column and the
closed, lower end of a narrow
vertical tube of uniform bore. The upper end of the tube is open
to the atmosphere
(atmospheric pressure = 76 cm of mercury). The lengths of the
mercury and the trapped gas
are 20 cm and 43 cm, respectively. What will be the length of
the gas column when the tube
is tilted slowly in a vertical plane through an angle of 60°?
Assume the temperature to be
constant.
9. Find the density of air at any height and hence the height at
which it is halved. Assume
that the temperature remains fixed throughout the atmosphere.
The pressure at the earth's
surface is = 1.012 105 − = 1.293
−
