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Elasticity Stress and Strain
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Elasticity Stress and Strain
Elasticity Stress and Strain
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1
Question
When does deformation occur in a solid body?
1:56
Answer
Deformation occurs when an external force changes the body’s shape, size, or both.
2
Question
How does an elastic body respond after the deforming force is removed?
3:08
Answer
An elastic body regains its original shape and size after the force is removed.
3
Question
How does a plastic body respond after the deforming force is removed?
4:21
Answer
A plastic body does not regain its original shape and size, so the deformation remains permanent.
4
Question
How do elastic and plastic deformation differ?
4:40
Answer
Elastic deformation is temporary and disappears after force removal. Plastic deformation produces a permanent change in shape or size.
5
Question
Why is steel considered more elastic than rubber in physics?
6:04
Answer
Elasticity is directly related to stiffness. Steel is stiffer and therefore has greater elasticity than rubber.
6
Question
What happens to a rubber chair under a sustained heavy load?
6:21
Answer
It may initially return to its original shape, but a sufficiently long load can produce permanent deformation.
7
Question
Which property allows a body to retain its deformed shape permanently?
7:26
Answer
Plasticity allows a body to retain its deformed shape permanently.
8
Question
Which materials are given as examples of plastic bodies?
7:42
Answer
Putty, mud, and clay are given as examples of plastic bodies.
9
Question
How is stress defined in terms of restoring force and area?
8:18
Answer
Stress is the restoring force developed per unit area of the body’s cross-section.
10
Question
Which formula represents stress in the lecture?
9:27
Answer
Stress is given by (F/A), where F is force and A is area.
11
Question
Which SI unit is used for stress?
9:41
Answer
Stress is measured in newtons per square metre, N/m².
12
Question
Which three types of stress are introduced?
9:58
Answer
The three types are longitudinal stress, shearing stress, and hydraulic or bulk stress.
13
Question
How does longitudinal stress affect a body?
10:57
Answer
Longitudinal stress acts perpendicular to the cross-sectional area and changes the body’s length.
14
Question
How do tensile and compressive stress differ?
11:15
Answer
Tensile stress increases a body’s length. Compressive stress decreases its length.
15
Question
How does shearing stress act on a solid body?
12:04
Answer
Shearing stress acts parallel or tangential to the surface, causing adjacent layers to slide over one another.
16
Question
What changes does shearing stress produce in a body?
13:03
Answer
Shearing stress changes the body’s shape without changing its volume.
17
Question
How does hydraulic or bulk stress act on an object?
13:28
Answer
It acts perpendicular to the surface in every direction and changes the object’s volume.
18
Question
How do shape and volume respond differently to bulk stress?
14:10
Answer
Under bulk stress, the shape remains the same while the volume changes.
19
Question
A wire supports a weight w over cross-sectional area A. What longitudinal stress develops?
15:12
Answer
The longitudinal stress is w/A because the stated weight w is already the applied force.
20
Question
How is strain defined for a deforming body?
16:17
Answer
Strain is the ratio of the change in dimension to the original dimension.
21
Question
Why is strain a dimensionless quantity?
16:54
Answer
Strain is a ratio of two dimensions with the same units, so the units cancel.
22
Question
Which formula gives longitudinal strain?
17:57
Answer
Longitudinal strain is Δl/l, the change in length divided by the original length.
23
Question
Which formula gives shearing strain for a displaced block?
20:23
Answer
Shearing strain is Δx/l, which may also be written as tan θ.
24
Question
Why can tan θ be approximated as θ in shearing strain?
20:45
Answer
For a very small angle, the mathematical approximation tan θ ≈ θ is used.
25
Question
Which formula gives volumetric strain?
21:01
Answer
Volumetric strain is ΔV/V, the change in volume divided by the original volume.
26
Question
What strain is produced when a solid sphere is immersed in a fluid?
21:50
Answer
A volumetric strain is produced because fluid force acts on the sphere in every direction and changes its volume.
27
Question
A 2-metre wire is stretched by 0.4 mm. What strain is produced?
22:07
Answer
The strain is 2 × 10⁻⁴ and has no unit, using ε = Δl/l = (0.4 × 10⁻³ m)/(2 m).
28
Question
What relationship does Hooke’s law establish between stress and strain?
23:32
Answer
Within the relevant elastic range, stress is directly proportional to strain: stress = k × strain.
29
Question
How is the modulus of elasticity defined within the elastic limit?
25:02
Answer
It is the ratio of the stress to the corresponding strain of a material within its elastic limit.
30
Question
What does the elastic limit represent for a material?
27:11
Answer
The elastic limit is the maximum stress up to which the material completely regains its original shape and size after force removal.