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ALFA PHYSICS CLASSES
Q.1
Q.2
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Q.5
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Q.7
Q.8
Q.9
The height of mercury barometer is 75cm at sea
level and 50cm at the top of the hill. Ratio of
density of mercury to that of air is 104. The
height of hill is
[a] 250m
[b] 1.2km
[c] 1.25km
[d] 750m
A closed compartment containing gas is moving
with some acceleration in horizontal direction.
Neglect the effect of gravity. Then the pressure
in the compartment is
[a] same everywhere
[b] lower on front side
[c] lower in rear side
[d] lower in upper side
Power required to raise 300 liters of water per
minutes through a height of 6m using a pipe of
diameter 2.4cm is
[a] 600W
[b] 400W
[c] 1000W
[d] 2000W
A solid shell looses half of its weight in water.
Relative density of the shell is 5. what fraction of
its volume is hollow?
[a] 3/5
[b] 2/5
[c] 1/5
[d] 4/5
Two spheres of 250cc each but of relative densities 0.8 and 1.2 are connected by a string and
the combination is immersed in a liquid. The
tension in the string is
[a] 5N
[b] 0.5N
[c] 1N
[d] 2N
A cylinder of mass m and density  hanging
from a string is lowered into a vessel of cross
sectional area s containing a liquid of density 
[< ] until it is fully immersed. The increase in
pressure at the bottom of the vessel is
[a] mg/s
[b] mg/s
[c] mg/s
[d] zero
A barometer reads 76cm of mercury. If the tube
is gradually inclined at an angle of 600 with vertical, keeping the open end immersed in the mercury reservoir, the length of mercury column will
be
[a] 152cm
[b] 76cm
[c] 38cm
[d] 383 cm
A cubical block of wood of specific gravity 0.5
and chunk of concrete of specific gravity 2.5 are
fastened together. The ratio of mass of concrete
to the mass of wood, which makes the combination to float with its entire volume submerged in
water, is
[a] 5/3
[b] 5/1
[c] 5/2
[d] 4/3
A satellite revolves around the earth. Air pressure inside the satellite is maintained at 76cm of
mercury. What will be the height of mercury column in a barometer tube 90cm long placed in
the satellite?
[a] 76cm
[b] 90cm
[c] zero
[d] can’t be predicted
Q.10 A glass tube 80cm long and open at both ends
is half immersed in mercury. Then the top of the
tube is closed and it is taken out of mercury. A
column of 20cm mercury then remains in the
tube. The atmospheric pressure [in cm of Hg] is
[a] 75
[b] 30
[c] 60
[d] 90
Q.11 Consider the barometer shown in
figure. Density of
mercury if . A
small hole is made
at point S as
shown. The mercury comes out from
this
hole
with
speed v equal to
[a] 2gH
[b] 2gh
[c] [2g(H-h)]
[d] none of these.
Q.12 The mean density of sea water is  and bulk
modulus is B. the change in density of sea water
in going from the surface of water to a depth h is
[a] B2/gh
[b] Bgh
[c] 2gh/B
[d] gh/B
Q.13 A ball floats on the surface of water in a container exposed to the atmosphere. Volume V1 of its
volume is inside water. If the container is now
covered and air is pumped out. Now let V2 by
the volume immersed in water. Then
[a] V1=V2
[b] V1> V2
[c] V2 > V1
[d] V2=0
Q.14 A block of volume V and density  is floating in a
liquid of density 2 filled in the vessel. Now the
vessel starts falling freely with acceleration ‘g’.
Then the volume of the block inside the liquid in
the following condition is
[a] V
[b] V/2
[c] arbitrary
[d] zero
Q.15 Mercury is poured in U tube. Temperature of
one side is 500C and level of mercury on this
side is h1. temperature of the other side is 1000C
and level of mercury on this is h2. then
[a] h1=h2
[b] h2 < h1
[c] h2 > h1
[d] h2=2h1
Q.16 A wooden cube is floating in water supports a
mass m=0.2kg on its top. When the mass is removed the cube rises by 2cm. The side of the
cube is
[a] 6cm
[b] 12cm
[c] 8cm
[d] 10cm
Q.17 A wooden plank is floating in a liquid. 50% of its
volume is inside the liquid when the vessel is
stationary. Percentage of the volume immersed
when the vessel moves upwards with the acceleration g/2
[a] 75%
[b] 25%
[c] 50%
[d] 33.33%
ALFA PHYSICS CLASSES
Q.18 A cubical block of wood of edge ‘a’ and density 
floats in water of density 2. The lower surface
of the cube just touches the free end of a massless spring of force constant k fixed at the bottom of the vessel. The weight W put over the
block so that it is completely immersed in water
without the weight is
[a] a[a2g+k]
[b]a[ag+2k]
[c]a[
a g
 2k ]
2
[d]a[a2g+ k/2]
Q.19 A cubical block of wood of specific gravity 0.5
and chunk of concrete of specific gravity 2.5 are
fastened together. The ratio of mass of concrete
to the mass of wood which makes the combination to float with its entire volume submerged in
water is
[a] 5/3
[b] 5/1
[c] 5/2
[d] 4/3
Q.20 A small block of wood of specific gravity 0.5 is
submerged at a depth of 1.2m in a vessel filled
with water. The vessel is accelerated upwards
with an acceleration of g/2. time taken by the
block to reach the surface, if it is released with
zero initial velocity is
[a] 0.6s
[b] 0.4s
[c] 1.2s
[d] 1s
Q.21 IF  is the density of the material of wire and  is
the breaking stress. The greatest length of the
wire that can hang freely without breaking is
[a] 2/g
[b] /g
[c]g/2
[d]/g
Q.22 Two wires A and B have same length and area
of cross section. But Young’s modulus of A is 2
times the Young’s modulus of B. then the ratio of
force constant of A to that of B is
[a] 1
[b] 2
[c] ½
[d] 2
Q.23 In case of liquid
[a] only bulk modulus is defined
[b] only bulk modulus and young’s modulus are
defined
[c] only bulk modulus and shear modulus are defined
[d] all the three moduli are defined
Q.24 A constant force F0 is applied on a uniform elastic string placed over a smooth horizontal surface as shown in figure. Young’s modulus of
string us Y and area of cross-section is S. the
strain produced in the string in direction of force
is
[a] FY/S
[b] F/SY
[c] F/2SY
[d] FY/2S
Q.25 A uniform rod of length L has mass per unit
length and area of cross section A. the elongation in the rod is L due to its own weight if it is
suspended from the ceiling of the room. The
Young’s modulus of the rod is
[a] 2gL2/Al
[b]gL2/2Al
[c]2gL/Al
[d]gl2/AL