3.
Which of the given statement is incorrect?
a)
Pressure is scalar quantity
b)
Liquid does not exert pressure
c)
Pressure is the cause of force.
d)
Hydraulic press is based on Archimedes’ principle.
4.
Which statement is true about law of floatation?
a)
Density of solid is equal to the density of liquid in which the solid is.
b)
Density of solid is greater than the density of liquid in which the solid
is.
c)
Weight of solid is lesser than the upthrust applied on the body by
liquid.
d)
Weight of solid is equal to the upthrust applied on the body by the
liquid.
5.
The weight of a body in air is 17 N and the weight of a body in water is
15 N. What will be the upthrust?
a) 17N b) 15N c) 7N d)
2N
6.
Which factor does not affect upthrust?
a) density of liquid b)
temperature of liquid
c) acceleration due to
gravity d) Shape of the
vessel in which a liquid is kept
7.
The pressure exerted by a liquid on the bottom of a container depends on
the:
a) Density of the liquid
only b)
Height of the liquid column only
c) Both a and b d)
None of these
8.
Which of the following liquids would exert the highest pressure at a
given depth?
a) Water b) Mercury c) Oil d) They would exert the same pressure
9.
Which principle or law is utilized to design ships and submarines?
a) Pascal's law b)
Newton's law c) Archimedes' principle
d) law of floatation
10.
Which law is given by the statement, “pressure applied at any point in an
enclosed vessel transmit equally in all direction”?
a)
a) Pascal’s law b) Boyle’s law c) Archimedes’ principle d) law of floatation
11.
Which force makes a heavy stone lighter in water?
a) Frictional force b) Gravitational force c) Buoyant force d)
viscous force
12.
The hull of a ship raise more in sea water than fresh water because ……………
a)
Sea water has less density than fresh water.
b)
Fresh water has lesser density.
c)
Sea water has more density than fresh water.
d)
A ship floats on water.
13.
The upthrust exerted on a stone by water is 5 N. if the stone weighs 20 N
in air, what is the weight of stone in water?
a) 15 N b) 20 N c) 10 N d) 5 N
Answers: 1(c), 2(a), 3(b),
4(d), 5(d), 6(d), 7(c), 8(b), 9(c), 10(a), 11(c), 12(c), 13(a)
Very
Short Questions:
1.
State law of floatation.
Law of
floatation states that an object floats on liquid medium only when it displaces
the liquid equal to its weight.
2.
What is upthrust or buoyancy?
When
a body is partially or wholly immersed in liquid, the liquid exerts an upward
force to the body which is called upthrust.
3.
State Archimedes principle.
Archimedes'
Principle states that when a body is partially or wholly immersed in liquid,
the upthrust is equal to weight of displaced liquid.
4.
Write two
condition when a substance floats on liquid.
Two condition when a
substance floats on a liquid are:
i)
When the density of substance is lesser than the density of
liquid,
ii) When the mass of the object is
equal to the mass of liquid displaced by it.
5.
Define pressure, write its formula and SI unit.
The
perpendicular force per unit area is pressure. Its formula is P =
6.
Mention two factors
which affect pressure due to liquid contained in a vessel.
Two factors
which affect pressure due to liquid contained in a vessel are depth of liquid
from its surface and density of liquid.
7.
Name two devices based on Pascal's law of liquid
pressure.
Two devices
based on Pascal's law of liquid pressure are:i) Hydraulic brake and ii)
Hydraulic lift
8.
What is
lactometer?
Lactometer is a
specially designed hydrometer used to measure the density of milk.
9.
Mention any two factors which effect the upthrust.
Two factors that
effect the upthrust are: (i) density of liquid and (ii) acceleration due to
gravity.
10. State Pascal's
law of liquid pressure.
It states that
the Pressure applied on a liquid kept in an enclosed vessel transmits equally in all
direction.
11. Write down the
formula to find the relative density of an object.
The formula to find the
relative density of an object is:
1.
What is one Pascal pressure.
When one Newton
force is applied perpendicularly in area 1m2 then pressure is called
one Pascal pressure.
2.
When a solid
object is dipped into a liquid, upthrust applied by the liquid on the object
and weight of the liquid displaced are equal in an experiment. Which principle
does this experiment prove?
This experiment
proves Archimedes’ principle.
3.
If a floating
ship has weight 1.5×106 N, how much water does it displace?
If a floating
ship has weight 1.5×106 N, it displaces 1.5×106 N of
water.
4.
Name a device based on law of floatation. Also
mention its one use.
Hydrometer is
the device based on the law of floatation. It is used to measure the density of
liquid.
5.
On which principle does hydraulic brake based? State
the principle also.
A
hydraulic brake is based on the Pascal's principle of liquid pressure. It
states that the liquid kept in a container transmits equal pressure
perpendicular to all direction.
1.
By which two properties of liquid it is used in
hydraulic brake?
Two properties of
liquid by which it is used in hydraulic brake are:
i)
Liquid cannot be compressed
ii)
liquid transmit pressure equally in all direction.
2.
What is hydrometer?
Hydrometer is a
device which is used to measure the density of liquids.
3.
What is the relationship between uptrhrust and the
density of liquid?
The upthrust exerted by
a liquid is directly proportional to the density of liquid.
Upthrust α density of
liquid
4.
What is hydraulic press?
Hydraulic press
is a simple machine based on Pascal's law of liquid pressure which converts
small force into large force and vice versa.
5.
Write the formula based on the Pascal's law.
Where P1 and
P2 are pressure on small piston and large piston respectively of
hydraulic machine. F1 and F2 are the force applied on
small and large piston and A1 and A2 are the
cross-sectional area of small and large piston respectively.
1.
At what condition a body floats on liquid?
A
body floats on liquid when it displaces liquid equal to its own weight.
2.
What number will be shown by hydrometer if sunk in
pure water?
Hydrometer
will show 1 number if it sunk in pure water.
3.
Which principle does hydraulic pressure obey? Write
the principle.
Hydraulic
pressure obey Pascal's law of liquid pressure. It states that the liquid kept
in a container transmits equal pressure perpendicular to all direction.
4.
Define one torr pressure.
The unit of
atmospheric pressure equivalent to 1mm of Hg or 103.22 Pa. is one torr
pressure.
5.
Define atomospheric pressure.
The pressure
exerted by atmospheric is called atmospheric pressure.
6.
Define normal atmospheric pressure, what is its
value?
The pressure
exerted by atmosphere in one square meter area at sea level is called normal
atmospheric pressure. Its value is equal to 1.01 x 105 Pa or 760mm
of Hg.
7.
What do you mean by 760mm of Hg?
It means that
the height of mercury column in baroeter at sea level is 760mm while measuring
atmospheric pressure.
8.
What is the relation between upthrust and density of
liquid.
The upthrust is
directly proportional to the density of liquid.
9.
Define density and relative density.
The mass per
unit volume is called density. The ration of density of a body to the density
of water at 4°C is called relative density.
10. "The weight of displaced liquid is equal to the weight
of floating objects." Which law does this statement belong to?
This statement belongs to law of floatation.
11. Pressure applied on a liquid enclosed in a vessel will be
transmitted equally in all direction perpendicular to the surface. Which law is
explained by this statement? Name the instrument which works on the basis of
this law?
Pascal's law of liquid pressure is
explained by this statement. The instrument which works on this principle is
hydraulic press.
12. What is the effect of density of a liquid on floatation of
an object?
13. Floatation
of an object increases with the increase in density of liquid.
Short Answer
Type Questions: [2 marks each]
1.
Write a condition in which the object having more
density than liquid floats on liquid.
When
the object can displace liquid equal to its own weight then the object having
more density than liquid floats on liquid.
2.
Why the ship can carry more load on the salty water
than fresh water?
In
salty water the density is more so that upthrust becomes more as we know that
upthrust is directly proportional to the density of liquid as a result the ship
can carry more load on salty water.
3.
It is easier to swim in sea water than in fresh
water. Why?
The
sea water has more density than the pure water. Due to this, when a man swims,
the upthrust acting on him due to sea water is greater than the upthrust acting
on him by fresh water. Because of this reason, it is easier to swim in sea
water than in fresh water.
4.
Why it is easier to pull a bucket of water from well until it is inside the water but
difficult out of water?
When
a bucket of water is in water, its weight is reduced due to the action of
upthrust of water. But, when it is pulled out of water, its weight is increased
due to the absence of upthrust of water and becomes heavy. Hence, it is easier
to pull a bucket of water from well until it is inside the water but difficult
when it is out of water due to the upthrust of water.
5.
What difference is observed if an egg is immersed in
pure water and in concentrated solution of salt? Write with reason.
6.
An egg sinks in pure water but floats on the concentrated
salt solution. This is because the density of salty water is more than the
fresh water, as we know that the upthrust is directly proportional to the
density. so being more upthrust due to salty water, an egg floats on it but
sinks in fresh water.
7.
It is
easier to lift a heavy stone inside water than air, why?
8.
When a stone is
inside water, its weight is reduced due to the upthrust exerted by water. But,
when it is in air, its weight is increased due to the absence of upthrust of
water and becomes heavy. Hence, it is easier to lift a stone in water but
difficult to lift in air.
9.
An iron
nail sinks in water but floats on mercury, why?
10.
An iron nail sinks in water because the density of iron nail
is more than water but it floats on mercury because the density of iron is
lesser than mercury.
11. What is the
difference between an empty sheep and loading ship moving in sea water?
12.
A loaded ship
has larger mass and it displaces more water to float on water but an empty ship
has less mass and it displaces less amount of water. Thus the hull of an empty
ship sinks less than the hull of a loaded ship.
13. Studs are made on the sole of football player's boot, why?
14.
The area of the studs of the football player's boot is less,
we have pressure is inversely proportional to the area. Hence, more pressure is
created on the ground by the studs. Due to high pressure the shoes properly get
stuck with the ground and does not allow the player to slip during the game.
15. Hydraulic press is called an instrument for multiplication
of force. Why?
Hydraulic press is called an
instrument for multiplication of force because the force applied on smaller
piston multiplies and a large force is exerted on large piston. According to
pascal's law;
Pressure on large piston (P1) = Pressure on small pistion (P2)
From the expression, we can say that
the force exerted on large piston is given by the product of pressure on small
piston and area of large piston. Hence due to this amplification, the applied
force is multiplied in the hydraulic press.
1.
Write the
difference in floatation of lactometer in pure milk and sugar dissolved milk.
Sugar dissolved salt has more
density than that of pure milk. Sugar dissolved milk exerts more upthrust of
lactometer than pure milk. So, the stem remains more above the milk in sugar
dissolved milk than pure milk.
2.
What is
the difference between the immersion of hydrometer in pure water and salty
water?
Hydrometer immerse more in pure
water than in salty water because the density of salty water is more than that
of pure water, which implies upthrust due to salty water is greater than pure
water and hydrometer immerse more in pure water than salty water.
3.
What
difference will you get from the flying of air filled balloon and the hydrogen
filled balloon?
An air filled balloon is heavier than
that of hydrogen filled balloon since the density of air is heavier than
hydrogen. Hence, upthrust due to air on the hydrogen filled balloon is more
thus, it flies to the greater height than that of air filled balloon.
43. Why does a stone sink in water?
A
stone sinks in water because its density is lesser than the density of water
and the upthrust exerted by water is lesser than the weight of stone.
44. Write the relation between upthrust and volume of displaced liquid. Lifting a stone in water is felt to be comparatively lighter, why?
Upthrust
is directly proportional to the volume of liquid displaced. Repeated.
45. The ship made by iron floats in water, but an iron nail
sinks, why?
The
shape and size of ship made by iron is so made that if can displace the liquid
equal to its weight. So a ship can float in water, but iron nail can't displace
the liquid equal to its weight so it sinks.
46. In given figure, which pressure is greater, AB or CD,
why?
Pressure
on Face CD is greater than AB because the pressure is directly proportional to
the depth and the depth is more on face CD.
47. The weight of any object
decreases inside water. Give reason. How much will an object lose in water?
Upthrust
force exerted by water reduces the downward force on the object. When an object
sinks in water the weight of object is lost and becomes light. So weight of an
object decreases inside water. An object lose weight equal to the weight of
water displaced by it.
48. A ship coming from sea enters
the river, will its hull sink more or less in river water? Give reason.
A
ship coming from sea enters the river, its hull will sink more in river water.
This is because the density of river water is lesser than the density of sea
water and it exerts less upthrust than sea water. As a result, hull of ship
will sink more in river water.
49. When a ball is pressed in water,
why does it try to come up?
When
the ball is pressed in water, it tries to come up because it experiences an
upthrust more than its weight.
50. What is the relation of upthrust
of a liquid and its density?
Upthrust
is directly proportional to the density of liquid. It means Upthrust increases
with the increase in density of liquid and vice versa.
51. What will be the effect in the
weight of displaced water if load is added into the ship float in the ocean?
Write with reason.
The
weight of water displaced increases and the hull will sink more when load is
added into the ship float in the ocean. This is because floating object
displaces liquid equal to their own weight. Here, when load is added into the
ship weight of ship increases and in order to float on water, it has to
displace more water.
52. If an object is
immersed in water, at what condition can it float in water, and at what
condition does it sink in water?
If
an object is immersed in water, it floats on water when its density is lesser
than the density of water or upthrust of water is more than the weight of the
object. It will sink in water, when its density is more than the density of water or if the upthrust
exerted by water is lesser than the weight of the object.
53. Constant weight hydrometer contains heavy bulb and narrow
stem, why?
The weight
of hydrometer contains heavy bulb to float in the liquid vertically and the
stem is made narrow for greater sensitivity.
54. The ice made
of water floats on water, why?
The density of ice is 0.9g/cm3 while the
density of water is 1g/cm3. Thus the density of ice is lesser than
the density of water. So, it floats on water.
55.
Air is filled in the tyres of bicycle, motorcycle, car, bus, etc. why ? Give
reason.
Ans: The air inside the tyres lifts
up the vehicles on the ground so that pressure of vehicles to the ground
decreases so air is filled in the tyres of vehicles.
56. Mention any
three applications of Pascal's law.
Ans: Any three applications of Pascal's law are
given below:
(i) Hydraulic press
(ii) Hydraulic lift
(iii) Hydraulic brake.
57. Define
hydraulic press and hydraulic lift.
Ans: The device which is used to
press the metal, grains etc and works on the basis of Pascal's law is called
hydraulic press.
Hydraulic lift : The device which
is used to lift the heavy load with small effort and works an the basis of
Pascal's law is called hydraulic lift.
58. Write the
use of hydraulic press and hydraulic lift.
Ans: The hydraulic press is used to obtain the oil
from seeds and also uses to press metal in order to convert metallic sheath.
Hydraulic lift is used to lift the heavy load with
small effort by cranes.
59. What are the
functions of hydrometer?
Ans: Followings are the functions of hydrometer.
(i) It measures the density of substance.
(ii) It measures the relative density of substances.
60.
Food gets cooked faster in pressure cooker, why?
Ans: The water boils when the
vapour pressure becomes equal to atmospheric pressure, inside the pressure
cooker the pressure becomes more so that water boils at high temperature as a
result pressure cooker cooks food faster.
61. What should
be the weight of displaced liquid to float an object of 375 kg.
Ans: According to law of floatation the weight of
displaced liquid should be 375 kg to float on that liquid.
62. Above the
certain height in the sky, the aeroplane can't fly, why?
Ans: The
aeroplane flies due to the difference of air pressure created by its fans,
above the certain height in the sky there is absence of air, so the aeroplane
can't fly above the certain height.
63. In given
figure the tanks A and B both contain equal amount of water but the height of
water in tank A is more than tank B, on which bottom the water exerts more
pressure, why?
Ans: The bottom of tank A experiences more liquid
pressure. The liquid pressure is directly proportional to the height or depth
of liquid column when acceleration due to gravity and density remain constant
and the depth of liquid is more in tank A. So, the bottom of tank A experiences
more pressure.
64.
In given figure, tank A and tank B contain salty water and fresh water
respectively. Both tanks contain the liquid upto equal height. Which
bottom experiences more liquid pressure out
of A and B? Why?
Ans: The bottom of tank A
experiences more liquid pressure. The liquid pressure is directly proportional
to the density of liquid when depth or height of liquid column and acceleration
due to gravity remain constant. In liquid of tank A the density is more than
the liquid of tank B. So. bottom of tank A experiences more liquid pressure.
65. Two tanks A
and B contain equal amount of water with equal height, but tank A is placed at
equator while tank B is placed at pole, which bottom experiences more liquid
pressure, why?
Ans: The bottom of tank B experiences more liquid
pressure because the liquid pressure is directly proportional to the
acceleration due to gravity when height and density remain constant, and we
know that the value of acceleration due to gravity is more at poles than
equator.
66.
Two tanks A and B contain equal amount of oil with equal height but the
temperature of tank A is 90°C and the temperature of tank B is 10°C, which
bottom experiences more liquid pressure, why?
The bottom of tank B experiences
more liquid pressure. The liquid pressure is directly proportional to the
density when height of liquid column and acceleration due to gravity remain
constant and the oil of tank B has more density due to its less temperature
than liquid of tank A. So, the bottom of tank B experiences more liquid
pressure.
67.
It is easier to cut with sharp knife than blunt one, why?
Ans: The area of sharp knife is
less than area of blunt one, we have pressure is inversely proportional to the
area i.e. Pα
68. Back wheels
of the tractors are made wider, why?
Ans: Tractors are used to plough in field, as the
wider wheels have more area, it exerts less pressure because pressure is
inversely proportional to the area i.e. Pα
69.
Dams are made wider at the bottom, why? Give reason.
Ans: Dams are made to hold the
water, at bottom the liquid pressure is more as we know that liquid pressure is
directly proportion to the depth of liquid i.e. Pαh when density and
acceleration due to gravity remain constant, to hold the more pressure at
depth, the bottoms are made wider.
70.
It takes less time to fill the bucket from the tap of lower floor than the tap
of upper floor, why ? Give reason.
Ans: At tap of lower floor the
depth or height of liquid column is more than the tap of upper floor. As we
know that liquid pressure is directly proportional to the depth of liquid i.e.
P α h when density and acceleration due to gravity remain constant, so water
comes with more pressure from the tap of lower floor, as a result it takes less
time to fill a bucket from the tap of lower floor than the tap of upper floor.
71. Camel can
walk on desert but horse can't, why? give reason.
Ans: The hoof of camel is boarder
than hoof of horse, so camel exerts less pressure while walking on desert, as
we know that pressure is inversely proportional to the area, i.e. Pα
72.
The blood pressure of our body is more at feet than at brain, why? Give reason.
Ans: As we know that liquid
pressure is directly proportional to depth or height liquid column. When
acceleration due to gravity, and density remain constant at feet, the height of
liquid column or height is more so blood pressure at feet is more than blood
pressure at brain.
73. In tank given in figure, which bottom experiences more liquid pressure out of A and B.
74. Why the dead
body of human floats in water?
Ans: Where person gets drawned in
water, he/she sinks as the cavity present inside the body is filled with water.
After some time it starts to decompose by the decomposer and produces the gases
like CH2 N2 etc, Hence the dead body floats in water.
75. Why does an egg float in salty water?
Ans: The
density of salty water is more than the fresh water, as we know that the
upthrust is directly proportional to the density. so the egg floats in salty
water.
76. From Archimedes principle give reason why a balloon
filled with hydrogen gas flies up?
Ans: The
balloon filled with hydrogen gas can easily displace the air more than its
weight. The upthrust becomes more than the weight of balloon. So it flies up.
22. Write the differences between a empty ship and loaded
ship moving on the sea.
|
Empty
Ship |
Loaded
Ship |
|
1.
Weight of displaced liquid is less. |
1.
The weight of displaced liquid is more. |
|
2.
The part immersed inside the water is less. |
2.
The part immersed in side the water is more. |
23. Differentiate between Archimedes principles and law of
flotation.
|
Archimedies
principle |
Law
of flotation |
|
1.When
an abject wholly or partially immersed in liquid experiences upthrust which is equal to the Wt. of
liquid displaced by it. |
1.
The floating object displaces its own Wt. of liquid.
|
|
2, It is applicable both in liquid &
in gaseous medium. |
2. It is applicable only in liquid but
not in gas. |
24. Differentiate between density and relative density.
|
Density |
Relative
density |
|
1.
The mass per unit volume is called density. |
I.
The ration of density of a body to the density of water at 4°C is called
relative density. |
|
2. Its SI unit is kg/m3. |
2.
It has no unit. |
|
3.
It is measured by constant weight hydrometer. |
3.
It is measured by constant immersion hydrometer. |
25. What
are the differences between constant immersion hydrometer and constant weight
hydrometer.
Ans:
|
Constant immersion hydrometer |
Constant weight hydrometer |
|
1. The hydrometer which measures the density by adding the
weights to immerse to the constant level is called constant immersion hydrometer. |
1. The hydrometer which measures the density by observing
the scale of the floating neck is called constant weight hydrometer. |
|
2. It measures the relative density. |
2. It measures the density of substance. |
26. Write two differences between upward and
downward thrust.
Two differences between upward and downward thrust
are:
|
Upward
thrust |
Downward thrust |
|
1. It
is the force acting in a liquid in upward direction. |
1. It is the force acting in a liquid in downward
direction. |
|
2. It
is caused by the buoyancy of the fluid. |
2. It is caused due to the gravity. |
27. Write two differences between thrust and upthrust.
|
Thrust |
Upthrust |
|
1. Thrust
act in downward direction. |
Upthrust acts in upward direction. |
|
2. Thrust
is caused by the force of an object moving through a liquid. |
Upthrust is caused by the buoyancy force of a
fluid. |
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