PHYSICS- +1

1. Mr. Sudhin Govind

2. The molecules are closely packed in a
definite order.
The inter molecular space is very small.
Solids can’t be compressed.
The inter molecular force in solids are very
strong.
Solids have a definite shape and size.
 Solids are crystalline or amorphous.
 The density of solids is slightly higher than
their liquid states.
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Mr.Sudhin Govind, AP,EEE

3. Solids are not perfectly rigid.
A rigid body generally means a hard solid
object having a definite shape and size.
But in reality solid bodies can be
stretched, compressed and bent. Solid
bodies are not perfectly rigid.
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Mr.Sudhin Govind, AP,EEE

4. The property of a body by virtue of which,
it tends to regain its original size and
shape when the applied force is removed
is known as elasticity and the deformation
caused is known as elastic deformation.
 Eg: - Steel is an elastic body
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Mr.Sudhin Govind, AP,EEE

5. The body which has no tendency to regain
its original shape and get permanently
deformed is called plastic body. This
property is known as plasticity.
 Eg: clay, wax, etc. are plastic bodies.
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Mr.Sudhin Govind, AP,EEE

6. A force which changes the length, shape
or volume of a body is called a deforming
force.
When an elastic body is subjected to a
deforming force, a restoring force is
developed in the body.
This restoring force is equal in magnitude
but opposite in direction to the applied
force.
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Mr.Sudhin Govind, AP,EEE

7. “The restoring force per unit area is known
as stress”
If F is the applied force and A is the area
of cross-section of the body,
then stress = F/A.
The S.I unit of stress is Nm-2 or Pascal
[Pa].
Its dimensional formula is ML-1T -2
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Mr.Sudhin Govind, AP,EEE

8. Three types,
• Linear Stress (longitudinal or tensile
stress)
• Volume stress (or Bulk stress)
• Shearing Stress (or tangential stress)
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Mr.Sudhin Govind, AP,EEE

9. Linear Stress (longitudinal or tensile
stress) It is the stress developed, when the
applied force produces a change in the
length of the body.
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Mr.Sudhin Govind, AP,EEE

10. Volume stress (or Bulk stress) It is the
stress developed in the body, when the
applied force produces a change in the
volume of the body.
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Mr.Sudhin Govind, AP,EEE

11. Shearing Stress (or tangential stress) It is
the stress developed in the body, when the
applied force produces, a change in shape
of the body.
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Mr.Sudhin Govind, AP,EEE

12. The effect of stress is to produce distortion
or a change in size, volume, and shape.
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Mr.Sudhin Govind, AP,EEE

13. The deforming force applied on a body
produces generally a change in its
dimensions and the body is said to be
strained.
 Strain is defined as the ratio of change in
dimension to the original dimension.
Strain = (Change in dimension)/
(Original dimension)
Strain has no unit and dimension
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Mr.Sudhin Govind, AP,EEE

14. Longitudinal Strain
Volume Strain
Shearing Strain
Lateral Strain.
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Mr.Sudhin Govind, AP,EEE

15. If the deforming force produces a change
in length, the strain produced in the body is
called longitudinal strain or tensile strain or
linear strain.
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Mr.Sudhin Govind, AP,EEE

16. If the deforming force produces a change
in volume, the strain produced in the body
is called volume strain.
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Mr.Sudhin Govind, AP,EEE

17. If the deforming force produces a change
in shape of the body without changing
volume, the strain produced is called
shearing strain.
Shearing Strain = tan Ø= dx/L
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Mr.Sudhin Govind, AP,EEE

18. If the deforming force produces a change
in diameter of the body.
Lateral train=d/d0
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Mr.Sudhin Govind, AP,EEE

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Mr.Sudhin Govind, AP,EEE

20. The stress strain curves vary from material
to material.
In the region OA, the curve is linear. In this
region Hooke’s law is obeyed. The body
regains its original dimensions, when the
applied force is removed. In this region the
solid behaves as an elastic body
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Mr.Sudhin Govind, AP,EEE

21. In the region OA, the curve is linear. In this
region Hooke’s law is obeyed. The body
regains its original dimensions, when the
applied force is removed. In this region the
solid behaves as an elastic body
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Mr.Sudhin Govind, AP,EEE

22. The point B in the curve is known as
elastic limit [yield point] and the
corresponding stress is known as yield
strength (Sy) of the material. If the load is
increased further (beyond elastic limit) the
body cannot regain its original dimension.
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Mr.Sudhin Govind, AP,EEE

23.  In the portion of the curve between C and D,
if the load is increased, strain increases
rapidly even for a small change in the stress.
 When the load is removed at some point, say
at C between B and D, the body doesn’t
regain its original dimension.
 The material is said to have a permanent set.
 The deformation is said to be plastic
deformation
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Mr.Sudhin Govind, AP,EEE

24. The point D on the graph corresponds to
the ultimate tensile strength (Su) of the
material.
Beyond the point D, additional strain is
produced even by a reduced applied force.
And fracture occurs at E.s
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Mr.Sudhin Govind, AP,EEE

25. If the ultimate strength and fracture points
D and E are close, the material is to be
brittle.
If D and E are far apart, the material is said
to be ductile.
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Mr.Sudhin Govind, AP,EEE

26. Substances like tissue of aorta, rubber,
etc., which can be stretched to cause large
strains are called elastomers.
These substances can be pulled to several
times the original length and still returns to
its original shape.
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Mr.Sudhin Govind, AP,EEE

27. According to Hooke’s law, “with in the
elastic limit stress is directly proportional to
stain”.
i.e., Stress α strain
Stress = K × Strain,
Where K is the proportionality constant
called the modulus of elasticity
K = (Stress)/(Strain)
S.I unit of ‘k’ is Nm-2 or Pascal [Pa]
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Mr.Sudhin Govind, AP,EEE

28.  Modulus of elasticity depends on:
• Nature of the material of the body
• Temperature.
 It is independent of the dimensions (i.e.,
length, volume etc) of the body.
Elastomer materials do not obey Hookes law
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Mr.Sudhin Govind, AP,EEE

29. Three types
1. Young's Modulus (Y)
2. Bulk Modulus (K)
3. Modulus of rigidity (ß)
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Mr.Sudhin Govind, AP,EEE

30.  The ratio of longitudinal stress to the
longitudinal strain is defined as the Young’s
modulus.

 Since strain is a dimensionless quantity, the
unit of Young’s modulus is same as that of
stress.
 i.e., N/m2 or Pascal.
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Mr.Sudhin Govind, AP,EEE

31. The ratio of the volume stress to the
corresponding volume strain is defined as
bulk modulus.
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Mr.Sudhin Govind, AP,EEE

32. The ratio of shearing stress to the shearing
strain is called the shear modulus of the
material.
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Mr.Sudhin Govind, AP,EEE

33. The reciprocal of bulk modulus is called
compressibility and is denoted by K.
S I unit :- Pa-1 or
Dimensional formula: - M-1LT2 .
The bulk modulus for solids is much larger
than that for liquids, which is again larger
than the bulk modulus for gases.
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Mr.Sudhin Govind, AP,EEE

34. When a longitudinal force is applied to a
rod , its length increase while it diameter
decrease.
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Mr.Sudhin Govind, AP,EEE

35. Poisons ratio is a dimensionless quantity
and has no unit.
Theoretical value of poisons ratio lies
between -1 and 0.5.
Practical value of poisons ratio lies
between 0 and 0.5. (never –ve)
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Mr.Sudhin Govind, AP,EEE

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Mr.Sudhin Govind, AP,EEE

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Mr.Sudhin Govind, AP,EEE

38.  The apparatus consist of two long straight
wires of same length and equal radius
suspended side by side from a rigid support.
 Since both the reference and experimental
wires are of the same material, their thermal
expansion will be the same.
 The weights placed in the pan exert a
downward force and stretch the experimental
wire under a tensile stress.
 The elongation of the wire (increase in
length) is measured by the vernier
arrangement.
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39.  Let r and L be the initial radius and length of the
experimental wire, respectively. Let M be the mass that
produced an elongation ∆L in the wire.
 The Young’s modulus of the material of the
experimental wire is given by,
 Using the above formula, the Young’s modulus of the
material of the experimental wire can be calculated.
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40. When a wire is stretched, then the work
done on the wire is stored in the form of
internal potential energy.
The amount of stored energy PE per unit
volume of a wire is called strain Energy.
The stretching force is increased uniformly
from 0 to F.
Avg = (0+F)/2=F/2
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41. Displacement of the free end =l
Work done= Favg*l
W=(Favg*l)/2
Volume= AL
Strain Energy =[(Favg*l)/2 ]/AL
U =1/2[Stress*strain]
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42. To find the thickness required for a metal
rope, to be used in cranes to pull up heavy
objects
To design a bridge for maximum safety.
To answer the question why maximum
height of a mountain on earth is limited to
approximately 10 Km.
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44. Mr. Sudhin Govind
Assistant Professor
Department of EEE
College of Engineering Trikaripur
Mob:09746600357
Email id: sudhinpnr@gmail.com
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