Introduction to Stress and Equilibrium in Materials

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Questions and Answers

What does tensile stress describe?

Intensity of force acting tangent to an area.

The point where the ratio P/A is at its minimum.

Normal force that 'pulls' or 'stretches' the area element. (correct)

Normal force that 'pushes' or 'compresses' the area element.

Shear stress is the intensity of force acting normal to an area.

False (B)

What is the primary focus of mechanics of materials?

The external loads applied to a body.

The internal loads and deformations within a body due to external loads. (correct)

The aesthetic design of structures.

The cost of materials used in construction.

What is the symbol used to represent shear stress?

τ (tau) Signup and view all the answers

Stress is defined as the area per unit force acting on that area.

False (B) Signup and view all the answers

In SI units, force is expressed in newtons (N) and area in square meters (m2). A N/m2 is a(n) _______

pascal Signup and view all the answers

What are the two fundamental requirements for the equilibrium of a rigid body?

Balance of forces and balance of moments Signup and view all the answers

Match the following terms with their descriptions:

Pascal (Pa) = Unit of pressure or stress (N/m²) Tensile Stress = Normal force pulling or stretching an area Compressive Stress = Normal force pushing or compressing an area Shear Stress = Force acting tangent to an area Signup and view all the answers

Which assumption is made when analyzing average normal stress in an axially loaded bar?

The bar remains straight and the cross-section remains flat during deformation. (A) Signup and view all the answers

A ______ is a diagram used to calculate the forces acting on a body.

free-body diagram Signup and view all the answers

Which of the following is NOT a type of internal resultant loading?

Applied pressure (A) Signup and view all the answers

Normal stresses are considered negative for tensile stresses and positive for compressive stresses.

False (B) Signup and view all the answers

The objective of a free-body diagram (FBD) is to determine the external forces acting on a body.

False (B) Signup and view all the answers

To find the maximum average normal stress in a bar with varying cross-sectional area and external loads, what ratio needs to be maximized?

P/A Signup and view all the answers

Match the following internal resultant loadings with their description:

Normal Force = Force acting perpendicular to the cross-sectional area Shear Force = Force acting parallel to the cross-sectional area Torsional Moment = Moment that tends to twist the member Bending Moment = Moment that tends to bend the member Signup and view all the answers

What is the formula for calculating average stress?

$Stress = Force / Area$ (B) Signup and view all the answers

What is the sign convention for axial force P when it causes compression in a member?

Negative (-) (C) Signup and view all the answers

Average normal stress is calculated by multiplying the internal resultant force P by the cross-sectional area A ($σ = P * A$).

False (B) Signup and view all the answers

When determining internal loading in an axially loaded member, at what point should the member be sectioned relative to its longitudinal axis?

Perpendicular Signup and view all the answers

The shear stress component acts in the ______ of the sectioned area.

plane Signup and view all the answers

In the context of shear stress, what does 'V' represent?

Internal resultant shear force at the section (A) Signup and view all the answers

Simple or direct shear is caused by an indirect action of an applied load.

False (B) Signup and view all the answers

For a double shear connection, how is the shear force 'V' related to the applied force 'F'?

V = F/2 Signup and view all the answers

Match the type of shear with its description:

Single shear = Cross-sectional area subjected to one connection Double shear = Cross-sectional area subjected to two connections Multiple shear = Cross-sectional area subjected to multiple connections with n connections Signup and view all the answers

What is the primary consideration when designing structural elements or mechanical components?

Designing the member so it won't fail during operation. (B) Signup and view all the answers

A Factor of Safety (F.S.) less than 1 is acceptable to avoid potential failure of a member.

False (B) Signup and view all the answers

What two steps are essential when using average normal stress and shear stress equations for analysis?

Draw free-body diagrams (FBD) and use equations of equilibrium (EoE). Signup and view all the answers

The average shear stress ($\tau_{avg}$) is calculated using the formula $\tau_{avg} = V/______$, where V is the internal shear force.

A Signup and view all the answers

Match the following steps with their corresponding descriptions when solving for average shear stress.

Draw free-body diagram = Isolate the member and show all external forces acting on it. Calculate cross-sectional area = Determine the area (A) of the surface that is being cut. Compute average shear stress = Using the formula τavg = V/A Signup and view all the answers

In the context of designing simple connections, what does the following formula represent? $A = \frac{P}{\sigma_{allow}}$

Area of a member subjected to normal force (C) Signup and view all the answers

When designing a simple connection, the cross-sectional area is not a key parameter.

False (B) Signup and view all the answers

What condition must be met regarding the force acting on a tension member?

The force has a line of action that passes through the centroid of the cross section. Signup and view all the answers

Flashcards

Stress

The intensity of the internal force acting on a material per unit area.

Normal Stress (σ)

Force per unit area acting perpendicular to a surface.