#Our Objective
To determine the density
of a solid (which is denser than water) by using a spring balance and a
measuring cylinder.
3.(verification of Archimedes’s principal)
#Our Objective
To establish the
relationship between the loss in weight of a solid and weight of water
displaced when the solid is fully immersed in the following solution.
GIVEN BELOW IS THE LAB MANUAL MATERIAL:
TERM – 2 (NOVEMBER –
MARCH)
Physics experiment:
1
(Pressure and area
relation)
#Our Objective
To observe and compare the pressure exerted by a
solid iron cuboid on sand while resting on its three different faces and to
calculate the pressure exerted in the three cases.
#The Theory
To study and compare the
pressure exerted by a solid iron cuboid on sand, we need to find its mass and
weight.
The mass of an object is a
fundamental property of the object; a numerical measure of its inertia; a fundamental
measure of the amount of matter in the object. The usual symbol for mass is 'm'
and its SI unit is kilogram.
In science, the weight of
an object is the force on the object due to gravity. Its magnitude (a scalar
quantity), often denoted by W, is the product of the mass m of the object and
the magnitude of the local gravitational acceleration g. Thus, W = mg. Since
the weight is a force, its SI unit is Newton.
Simply stated, weight is the force acting vertically downward. The weight of an
object is the force with which it is attracted towards the earth, that is:
F = m x g
An object's weight depends
on its environment, while its mass does not. The SI unit of weight is the
same as that of force, that is, Newton (N).The force acting on an object
perpendicular to the surface is called thrust. The effect of thrust depends on
the area on which it acts. Thus:
Thrust = F = m x g
The thrust on unit area is
called pressure. Thus:
pressure = thrust / area
SI unit of pressure is N/m2 or Nm-2 or pascal, denoted by Pa.
#Materials required:
solid iron cuboid, scale and dry sand filled tub.
#The Procedure:
As performed
in a real lab:
Fill ¾ ths of a tray with
dry sand and level it.
- Measure the dimensions of a solid iron
cuboid accurately using a scale. Mark the three faces of the cuboid as A,
B and C.
- Place the solid iron cuboid by the
surface A on the plane levelled sand in the tray.
- After a few minutes, remove the Iron
cuboid and you will see that it has made a depression in the sand.
- Measure the depth (depression) it has
made in the sand using the scale.
- Repeat the same procedure for the other
two surfaces.
#Observations:
Gravitational force on the
environment = …….. . m/s2
1.
Calculate the area occupied by each surface of the solid iron
cuboid.
- Area occupied by surface A in the sand
= .............cm2
- Area occupied by surface B in the sand
= ............. cm2
- Area occupied by surface C in the sand
= ............. cm2
2.
Calculate the pressure made by each surface of the solid iron
cuboid.
·
Pressure made by the surface A in the sand = ............. N
·
Pressure made by the surface B in the sand = ............. N
·
Pressure made by the surface C in the sand = ............. N
3.
Calculate the Depression.
·
Depression made by the surface A in the sand =
............. cm
·
Depression made by the surface B in the sand = ............. cm
·
Depression made by the surface C in the sand = ............. cm
#Learning outcomes
1.
The depression in sand is greater when the solid iron cuboid is
placed on its least surface area.
2.
The pressure exerted by the smallest surface area is greater than
the other surfaces with larger areas.
3.
Thus, the students understood the theories of force, area
pressure, depression and their dependence on each other.
#Precautions:
1.
Dried sand must be used.
2.
The tray must have
significant length and width.
- Appropriate cuboid of dimension must be
used.
Physics experiment: 2
(Calculation of density)
#Our Objective
To determine the density
of a solid (which is denser than water) by using a spring balance and a
measuring cylinder.
#The Theory
All matter has mass and
volume. Mass and volume are the physical properties of matter and may
vary with different objects The amount of matter contained in an object is
called mass. Its measure is usually given in grams (g) or kilograms
(kg). Volume is the amount of space occupied by an object. The units
for volume including liters (l), meters cubed (m3),
Consider two different
substances such as iron and cotton of same mass. It is observed that Iron will
occupy less volume as compared to cotton. This is due to their differences in
density. Density of Iron is more than that of cotton.
The mass of a unit
volume of a substance is called its density.
DENSITY OF SUBSTANCE = MASS OF SUBSTANCE / VOLUME OF SUBSTANCE
If D is the density of a
body of mass M and volume V, then
D = M/V
In S.I units density is
expressed in kg m -3.
Most of the substances
expand on heating and contract on cooling, but the mass remaining constant for
all cases. The density of most of the substances decreases with the increase in
temperature and increases with decrease in temperature. But water contracts
when cooled up to 40C but expands when cooled further below 40C . Thus the density of water is maximum at 40C.
Spring Balance:
It is a device used for the determination of gravitational mass of a body. It
works on the principle of Hooks law of elasticity which states that when a body is suspended from a vertical spring, the body produces
extension in the length of the spring proportional to its gravitational mass.
#Materials Required:
iron stand, measuring jar, steel bob, iron block, lock, stone spring balance.
#Procedure:
How to measure
the gravitational mass of a solid using a spring balance?
In real lab:
·
Take a metallic solid block.
·
Tie it with a thin strong thread to hang it on the hook of the
spring balance.
·
Note the least count of the spring balance.
·
Hang the block on the hook of spring balance. It is better to hang
the spring balance with the help of an iron stand or clamp stand so that it
remains static while noting the mass of the block.
·
Carefully observe the gravitational mass of the solid block and
note it down.
Now we need to
find the volume of the solid as you know,
Density, D = mass/ volume
a) for that:
·
Take a graduated glass cylinder of proper size and capacity. Fill
it with water up to a known volume level mark.
·
Tie the rectangular metallic block by a thin strong thread and
immerse it fully in water taken in the graduated cylinder. The block displaces
water and the water level rises. Note the position of water level (meniscus)
keeping the eye in horizontal position with the level (to avoid error due to
parallax).
·
Find the difference of two positions of the water level to find
volume of metallic block immersed.
.
#Observations:
Record your observation of
measurement of mass and volume :.
1. Gravitational
mass of the solid block, =...................g.wt
(by spring balance)
2. Volume of
the solid block by graduated cylinder =
...................ml(cm3).
When the experiment is
conducted in earth as environment, the mass of the object and gravitational
mass displayed on the spring balance is the same. But when we do it on another
planet like moon, mars, etc., the mass of object and gravitational mass are
different. The mass displayed in the spring balance is taken as gravitational
mass (w) of the object and the mass of object can be calculated by using the
formula.
Mass of
the object:
You can
calculate the density (D) of the given solid block (denser than water) with the
calculated mass and volume.
Mass of the solid,
(i) Mass of the solid (m) =
..................... g
(ii) volume of the solid
block (V) =...................cm3
(iii) Density (D) of the
solid block = Mass / Volume
D = mass/ volume
=......................
g/cm3
Least
count of the spring balance:
1 division = _____ g
#Result:
The density of the given
solid (heavier than water) is .................... g/cm3./p>
#Precautions:
1.
Always used a thread of least weight and volume to tie the solid
block.
2.
The solid block should be dried before measuring mass and volume.
3.
The indicator of the spring balance should be at zero before
measuring the mass of the solid.
4.
The solid block should be completely immersed in water of the
measuring cylinder before observing its volume and water of the measuring
cylinder should not spill.
5.
The solid block should not touch the brim and sides of the beaker.
#Learning outcomes
1.
The student will
understand the concepts of mass, volume and density of an object.
2.
The student can
calculate density of a solid heavier than water by measuring its mass and
volume.
Physics experiment: 3
(verification of Archimedes’s principal)
#Our Objective
To establish the
relationship between the loss in weight of a solid and weight of water
displaced when the solid is fully immersed in the following solutions:
- Tap water
- Strong salty water
This can be done by using
at least two different solids in the experiment.
#The Theory
When a metallic block
is immersed in water (or any other liquid), four vertical forces act upon the
block below the surface of water. These forces can be grouped into two types of
forces.
1.
Downward forces
a.
The weight of the block.
b.
The downward thrust due to pressure of the liquid on the upper
surface of the block.
2.
Upward forces
a.
The tension of the spring, which measures the apparent weight.
b.
The upward thrust due to liquid present below the lower surface of
the block. This upward thrust is known as Buoyancy.
What happens
to the weight of a body when immersed in water?
The more a body is immersed
in water, the more the weight of the body decreases. The weight of the body is
least when it is completely immersed in water. This means that loss in weight of the body increases as it is completely immersed in
water.
When a body is partly or
completely immersed in water (or any other liquid), then:
Loss in weight of body =
Weight of water (liquid) displaced by the body = Buoyant force or upthrust
exerted by water (any liquid) on the body.
It was Archimedes who first
observed that bodies lose their weight when immersed in water. He proposed a
principle based on his observation that is now known as the Archimedes'
Principle.
What does
Archimedes' Principle state?
The Principle states that:
“A body immersed in a liquid loses weight by an amount equal to the
weight of the liquid displaced.”
Archimedes principle also states that: “When a
body is immersed in a liquid, an upward thrust, equal to the weight of the
liquid displaced, acts on it.”
Thus, when a solid is fully immersed in a liquid, it loses weight which is
equal to the weight of the liquid it displaces.
WEIGHT OF THE SOLID IN AIR - WEIGHT OF THE SOLID IMMERSED IN LIQUID = LOSS OF WEIGHT IN SOLID
LOSS OF WEIGHT IN SOLID = WEIGHT OF DISPLACED WATER
The more the density of
liquid in which the solid is immersed, the less is the weight of the liquid
displaced on immersing the solid.
Does a body
float?
Some bodies, if dropped in
water, sink, such as a stone or a metallic needle. On the other hand,
some bodies, even of the same weight as that of those that sink, float on
water. This can be proved through the Laws of Flotation.
What does the
Law of Flotation state?
A body will float if the
weight of the body is equal to the weight of the liquid displaced.
If the weight of the immersed body is more than the weight of the water
displaced, the body will sink.
#Materials Required:
Iron stand, weighing balance, wooden base, 500 ml beaker with tap water, 500 ml beaker with salt water, overflow beaker, bob, spring balance.
#The Procedure: .
As done in a
real lab :
We’ll
first prepare the strong salty water:
Take 400 ml of tap water in
a 500 ml beaker, add some common salt to it and stir well. Go on adding salt to
the water and dissolve it by stirring the solution with a glass rod until some
of the salt remains undissolved in the beaker. Decant the strong (saturated)
salty water and store for further use.
Now to
start:
1.
Hang a spring balance on an iron stand using a clamp.
2.
Note the least count of the spring balance.
3.
Take one of the solid blocks (S1) and
weigh it by hanging it on the hook of the spring balance using a thread. Find
the weight of the solid in air (Wa) and note
it.
4.
Take two beakers (each of 250 ml) and mark them as A and B. Weigh
them on a balance separately and note down the mass of beaker A and B.
5.
Take an overflow can and fill it with water to the brim of the
outlet and place beaker A below the overflow outlet of the can to collect the
displaced water. Now, start lowering the metallic block (S1), still
attached to the spring balance into the water of the overflow can.
6.
Note the loss of weight of the metallic block as it gets
completely immersed in the water. Weigh beaker A which contains the displaced
water and note the mass. To find the mass of the water displaced, subtract the
initial mass of beaker A (without displaced water) from the present mass of the
beaker A (containing displaced water).
WEIGHT OF THE BEAKER A + DISPLACED WATER - WEIGHT OF THE EMPTY BEAKER A = WEIGHT OF DISPLACED WATER.
7.
Repeat the experiment using the metallic block S1 by completely immersing it in the strong salty water in the
overflow can. Note the loss in weight S1 by immersing it in the strong salt solution. Find the mass of the
salt solution displaced and collected in the beaker.
WEIGHT OF THE BEAKER B ALONG WITH DISPLACED SALT SOLUTION - WEIGHT OF THE EMPTY BEAKER B = WEIGHT OF THE DISPLACED WATER
#Observations:
- Weight of metallic block S1 in air =
.................. g wt.
- Mass of empty beaker = ............ g.
- Weight of the block (S1) after
immersed in solution = ................. g wt.
- New mass displayed in the digital
balance = ................. g.
- Loss of weight of block in air =
.............. g wt.
- Mass of water displaced (m) =
...................... g.
- Weight of solution displaced = m x g =
............ g wt.
Least count of
the spring balance :
1 division = _________g.wt
#Precautions:
1. The string used to hang the spring balance should
have negligible weight.
2. The metallic block should be gradually immersed in
water.
3. Reading of spring balance should be taken only when
it is stable.
4. When immersing the metallic block in water, care
should be taken that displaced water does not spill.
#Learning outcomes
The results obtained
confirm Archimedes' Principle. They prove that:
1.
When a body is partly or completely immersed in water, it loses
weight.
2.
A body loses its maximum weight when it is completely immersed in
water.
3.
When a body is partly or completely in water then:
- Loss in weight of the body = Weight of
water displaced by the body = Buoyant Force or up-thrust exerted by water
on the body.
- Volume of the water displaced = Volume
of the body immersed in water.
NOTE:
KINDLY DRAW THE IMAGES RELATED TO EXPERIMENT AS WELL
