CBSE Class 11 > Class 11 Videos > Stress - Mechanical Properties of Solids
Stress - Mechanical Properties of Solids Video Lecture - Class 11
FAQs on Stress - Mechanical Properties of Solids
| 1. What are the mechanical properties of solids? |  |
Ans. The mechanical properties of solids refer to the characteristics that describe how a solid material responds to external forces or loads. These properties include elasticity, plasticity, strength, hardness, stiffness, toughness, and ductility.
| 2. What is stress in the context of mechanical properties of solids? | |
Ans. Stress is a measure of the internal resistance of a solid material to external forces or loads applied to it. It is defined as the force per unit area acting on a material. Stress can cause deformation or change in shape and size of the material.
| 3. How is stress calculated in mechanics? | |
Ans. Stress is calculated by dividing the applied force by the cross-sectional area of the material. The formula for stress is Stress = Force/Area. The SI unit of stress is Pascal (Pa), which is equal to one Newton per square meter (N/m²).
| 4. What is strain in the context of mechanical properties of solids? | |
Ans. Strain is a measure of the deformation or change in shape and size of a solid material due to the applied stress. It is defined as the ratio of the change in length or dimension of the material to its original length or dimension. Strain has no unit as it is a dimensionless quantity.
| 5. What is the relationship between stress and strain in materials? | |
Ans. The relationship between stress and strain in materials is described by the concept of elasticity. When stress is applied within the elastic limit of a material, it undergoes proportional deformation or strain. This relationship is represented by Hooke's law, which states that the stress is directly proportional to the strain. However, beyond the elastic limit, the material exhibits plastic deformation, and the stress-strain relationship becomes nonlinear.
Text Transcript from Video
hello friends this video on mechanical
properties of solid part 2 is brought to
you by exam feel calm no more fear from
exam please make sure that you have
watched part 1 before going ahead with
part 2 now let us learn what is stress
stress is the restoring force per unit
area so this could be a new term to you
restoring force so what is restoring
force what happens generally it is
whenever you apply an external force on
a body to deform it that means whenever
you apply some external force to change
the shape of a body putting out any kind
of deformation into the body there is a
restoring force which develops on the
body in the opposite direction let us
suppose this is a this is an elastic
bone or a ball made of rubber which can
be deformed quite easily now you apply
an external force to deform the whole I
mean you want to compress it what
happens at the same instant there is a
force which develops on the ball which
acts in the opposite direction you are
applying the force in this direction and
this force which develops in the ball it
acts in the opposite direction
however the both the forces are equal in
magnitude so they are equal and opposite
forces so this opposite force which
develops on the ball when an external
force is applied on it to deform it is
known as the restoring force so this
restoring force per unit area is known
as stress so basically force is I mean
if we write it mathematically it is
nothing but force per unit area so the
SI unit of force is Newton per meter
square
Newton for force meter square foot area
or it is asked them now you must be
thinking that this it is is this all the
same as that of pressure because of a
pressure is force per unit area but in
that case force is the force which you
apply but in this case this force is
nothing but the restoring force which
develops inside the body because of the
force which you were
right so stress is restoring force per
unit area there are different types of
stress longitudinal stress tangential or
shearing stress and hydraulic stress so
we will talk about these three kinds of
stress longitudinal stress tangential or
shearing stress and hydraulic stress now
within longitudinal stress we will have
two sub categories that is tensile
stress and compressive stress now we
will discuss each of the types of stress
in detail one by one so let's start with
longitudinal stress so now we will see
what is longitudinal stress now what can
you guess from the name longitudinal
longitudinal word has come from the term
long hinge it right
what is longitude it is something like
the longitudinal lines of the earth
something like this so something which
is lengthwise so when I talk of
longitudinal stress it is basically
force restoring force per unit area when
the force applied is normal to the cross
sectional area of the cylindrical body
let us suppose this is an this is an
object which we want to deform so when
we apply a force perpendicular to the
cross sectional area what is the cross
sectional area of the cylinder this is
the cross sectional area right so this
is the cross sectional area right so
even we have this is the cross section
area again this is the cross sectional
area so when we apply a force
perpendicular to this area and there is
a restoring force which develops in the
cylinder in the opposite direction so
that restoring force per unit area is
known as the longitudinal stress now
this is known as longitudinal stress
because I'm due to the effect of this
stress there is a change in length of
the cylinder you just try to think of it
in this way it is suppose we have a
cylinder which is made up of something
like rubble which can be easily
stretched now what I do
I take a small threat and die a heavy
some heavy mass let us say some heavy
box containing a lot of things and hang
it to the cylinder now once it is left
what happens is it goes down and the
cylinder gets stretched so what happened
if you observe very carefully initially
this was the length of the cylinder
right this is the initial length of the
cylinder now after it gets stretched the
length got increased by Delta L so this
is the increase in the length due to the
stress so since there is a change in the
length of the cylinder
therefore to this kind of stress is
known as long e to general stress so
what is longitudinal stress once again
it is restoring force per unit area when
the force is applied perpendicular to
the cross-sectional area of the body now
as I told you
under longitudinal stress we have two
kinds of stress when is tensile stress
and the other one is compressive stress
so what is tensile stress when the force
is applied to stretch the cylinder as I
told you there are two things which we
can do let us suppose we have a cylinder
if we push it from both the sides to
stretch it the length will increase
similarly if we push it from both the
ends to contract it so it will get
compressed right so these are the two
kinds of stress which falls under
longitudinal stress then we apply a
force to stretch the cylinder somewhat
like this you imagine it in this way
that on both sides you are pushing as
hard from both the sides so what happens
the length of the cylinder increases so
this is known as tensile stress so
tensile stress is the longitudinal
stress wherein the length of the
cylinder increases
whereas compressive stress as the name
suggests there has to be some
compression associated with it so in
this case the force is applied to
compress the cylinder you are applying
the force in this direction therefore
there will be a restoring force which
will be
ting in the opposite direction but the
result of the forces is that the
cylinder gets compressed so this is a
compressive stress now let us see what
is tangential or shearing stress as the
name suggests tangential stress is
something when we apply the force
injection to the cross sectional area
that is restoring force per unit area
when the force applied is parallel to
the cross sectional area of the body in
longitudinal stress we found we saw that
the external force was applied
perpendicular to the cross sectional
area so in this case it is basically the
restoring force per unit area when the
force applied is parallel to the cross
sectional area of the body so in this
case what happens is there is a relative
displacement which occurs between the
opposite faces of the body in
longitudinal stress what was the result
the result was that there was an
increase in length of the body but in
case of tangential stress what happens
is since we apply the force parallel to
the cross sectional area there is a
relative displacement which occurs
between the opposite faces of the body
let us take this example it is suppose
you have to surrender in this case you
apply a force in this direction right so
you are applying a force parallel to the
cross sectional area so this is the
cross sectional area you are applying a
force in this direction which is
parallel to the cross sectional area so
what happens there is basically the
movement which we are showing here it is
not external movement it is basically a
movement which takes place between the
opposite faces that is or opposite faces
have a relative motion with each other
so these kind of stress is known as
tangential stress or it is also known as
shearing stress this is called
contention because the force is applied
tangential to the cross sectional area
so in this case what happens is when you
apply this force there is a restoring
force which acts in the opposite
direction the third type of stress is
the hydraulic stress the term hydraulic
itself shows that it must be something
related to water it is derived from the
term hydro
right so hydraulic stress is the
restoring force per unit area
when forces applied by a fluid on the
body when the force is applied by a
fluid then that kind of stress is known
as the hydraulic stress let us take this
example let us suppose you have a ball
which is made up of something like
rubber that can be compressed now if
that boy is dipped inside a river or see
what happens due to the pressure of the
water there is a force which acts on
this ball from all directions so from
all your directions uniformly a pressure
act a force acts on this point because
of which this boy things to point rapid
if you see very carefully initial size
was bigger but later the shape remains
the same where there is a very slight
contraction the contraction is so small
that it is you can Ann spirit you can it
cannot be seen with your eye but then
there is a very minut contraction which
happens due to the force exerted by the
water so these stress that is because of
this force there is and there is a
restoring force which develops in the
ball which is equal in magnitude to that
force applied but in opposite direction
so this restoring force per unit area
which which arises because of the force
applied by the fluid is known as
hydraulic stress thank you please visit
exam viacom to watch free educational
videos try 3 online tests get the best
quality study materials study from the
best tutors and mentors and much more
thank you once again
properties of solid part 2 is brought to
you by exam feel calm no more fear from
exam please make sure that you have
watched part 1 before going ahead with
part 2 now let us learn what is stress
stress is the restoring force per unit
area so this could be a new term to you
restoring force so what is restoring
force what happens generally it is
whenever you apply an external force on
a body to deform it that means whenever
you apply some external force to change
the shape of a body putting out any kind
of deformation into the body there is a
restoring force which develops on the
body in the opposite direction let us
suppose this is a this is an elastic
bone or a ball made of rubber which can
be deformed quite easily now you apply
an external force to deform the whole I
mean you want to compress it what
happens at the same instant there is a
force which develops on the ball which
acts in the opposite direction you are
applying the force in this direction and
this force which develops in the ball it
acts in the opposite direction
however the both the forces are equal in
magnitude so they are equal and opposite
forces so this opposite force which
develops on the ball when an external
force is applied on it to deform it is
known as the restoring force so this
restoring force per unit area is known
as stress so basically force is I mean
if we write it mathematically it is
nothing but force per unit area so the
SI unit of force is Newton per meter
square
Newton for force meter square foot area
or it is asked them now you must be
thinking that this it is is this all the
same as that of pressure because of a
pressure is force per unit area but in
that case force is the force which you
apply but in this case this force is
nothing but the restoring force which
develops inside the body because of the
force which you were
right so stress is restoring force per
unit area there are different types of
stress longitudinal stress tangential or
shearing stress and hydraulic stress so
we will talk about these three kinds of
stress longitudinal stress tangential or
shearing stress and hydraulic stress now
within longitudinal stress we will have
two sub categories that is tensile
stress and compressive stress now we
will discuss each of the types of stress
in detail one by one so let's start with
longitudinal stress so now we will see
what is longitudinal stress now what can
you guess from the name longitudinal
longitudinal word has come from the term
long hinge it right
what is longitude it is something like
the longitudinal lines of the earth
something like this so something which
is lengthwise so when I talk of
longitudinal stress it is basically
force restoring force per unit area when
the force applied is normal to the cross
sectional area of the cylindrical body
let us suppose this is an this is an
object which we want to deform so when
we apply a force perpendicular to the
cross sectional area what is the cross
sectional area of the cylinder this is
the cross sectional area right so this
is the cross sectional area right so
even we have this is the cross section
area again this is the cross sectional
area so when we apply a force
perpendicular to this area and there is
a restoring force which develops in the
cylinder in the opposite direction so
that restoring force per unit area is
known as the longitudinal stress now
this is known as longitudinal stress
because I'm due to the effect of this
stress there is a change in length of
the cylinder you just try to think of it
in this way it is suppose we have a
cylinder which is made up of something
like rubble which can be easily
stretched now what I do
I take a small threat and die a heavy
some heavy mass let us say some heavy
box containing a lot of things and hang
it to the cylinder now once it is left
what happens is it goes down and the
cylinder gets stretched so what happened
if you observe very carefully initially
this was the length of the cylinder
right this is the initial length of the
cylinder now after it gets stretched the
length got increased by Delta L so this
is the increase in the length due to the
stress so since there is a change in the
length of the cylinder
therefore to this kind of stress is
known as long e to general stress so
what is longitudinal stress once again
it is restoring force per unit area when
the force is applied perpendicular to
the cross-sectional area of the body now
as I told you
under longitudinal stress we have two
kinds of stress when is tensile stress
and the other one is compressive stress
so what is tensile stress when the force
is applied to stretch the cylinder as I
told you there are two things which we
can do let us suppose we have a cylinder
if we push it from both the sides to
stretch it the length will increase
similarly if we push it from both the
ends to contract it so it will get
compressed right so these are the two
kinds of stress which falls under
longitudinal stress then we apply a
force to stretch the cylinder somewhat
like this you imagine it in this way
that on both sides you are pushing as
hard from both the sides so what happens
the length of the cylinder increases so
this is known as tensile stress so
tensile stress is the longitudinal
stress wherein the length of the
cylinder increases
whereas compressive stress as the name
suggests there has to be some
compression associated with it so in
this case the force is applied to
compress the cylinder you are applying
the force in this direction therefore
there will be a restoring force which
will be
ting in the opposite direction but the
result of the forces is that the
cylinder gets compressed so this is a
compressive stress now let us see what
is tangential or shearing stress as the
name suggests tangential stress is
something when we apply the force
injection to the cross sectional area
that is restoring force per unit area
when the force applied is parallel to
the cross sectional area of the body in
longitudinal stress we found we saw that
the external force was applied
perpendicular to the cross sectional
area so in this case it is basically the
restoring force per unit area when the
force applied is parallel to the cross
sectional area of the body so in this
case what happens is there is a relative
displacement which occurs between the
opposite faces of the body in
longitudinal stress what was the result
the result was that there was an
increase in length of the body but in
case of tangential stress what happens
is since we apply the force parallel to
the cross sectional area there is a
relative displacement which occurs
between the opposite faces of the body
let us take this example it is suppose
you have to surrender in this case you
apply a force in this direction right so
you are applying a force parallel to the
cross sectional area so this is the
cross sectional area you are applying a
force in this direction which is
parallel to the cross sectional area so
what happens there is basically the
movement which we are showing here it is
not external movement it is basically a
movement which takes place between the
opposite faces that is or opposite faces
have a relative motion with each other
so these kind of stress is known as
tangential stress or it is also known as
shearing stress this is called
contention because the force is applied
tangential to the cross sectional area
so in this case what happens is when you
apply this force there is a restoring
force which acts in the opposite
direction the third type of stress is
the hydraulic stress the term hydraulic
itself shows that it must be something
related to water it is derived from the
term hydro
right so hydraulic stress is the
restoring force per unit area
when forces applied by a fluid on the
body when the force is applied by a
fluid then that kind of stress is known
as the hydraulic stress let us take this
example let us suppose you have a ball
which is made up of something like
rubber that can be compressed now if
that boy is dipped inside a river or see
what happens due to the pressure of the
water there is a force which acts on
this ball from all directions so from
all your directions uniformly a pressure
act a force acts on this point because
of which this boy things to point rapid
if you see very carefully initial size
was bigger but later the shape remains
the same where there is a very slight
contraction the contraction is so small
that it is you can Ann spirit you can it
cannot be seen with your eye but then
there is a very minut contraction which
happens due to the force exerted by the
water so these stress that is because of
this force there is and there is a
restoring force which develops in the
ball which is equal in magnitude to that
force applied but in opposite direction
so this restoring force per unit area
which which arises because of the force
applied by the fluid is known as
hydraulic stress thank you please visit
exam viacom to watch free educational
videos try 3 online tests get the best
quality study materials study from the
best tutors and mentors and much more
thank you once again
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Apr 20, 2026 Last updated
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