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*statics > Intro, Terminology, and Ch. 2 > Flashcards

Intro, Terminology, and Ch. 2 Flashcards

1
Q

What is Statics?

A

the study of the equilibrium of bodies under action of forces

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2
Q

What is Dynamics?

A

the study of objects in motion

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3
Q

What are two other areas of mechanics besides Statics and Dynamics?

A
  • Mechanics of Materials

- Fluid mechanics

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4
Q

What is Newton’s 1st Law?

A

If an object is in motion, it will remain in motion. If an object is at rest, it will remain at rest.
(i.e. When sum of forces acting on an object is zero, the object will remain at rest if initially at rest.)

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5
Q

What is Newton’s 2nd Law?

A

Sum of forces = mass x acceleration

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6
Q

What is Newton’s 3rd Law?

A

Forces exerted by two objects on each other are equal in magnitude and opposite in direction.
(i.e. for every action there is an equal and opposite reaction)

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7
Q

What are the two basic models used in Statics?

A
  • Particle

- Rigid bodies

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8
Q

Particle

A

has mass but no size or shape

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9
Q

What is the acceleration due to gravity?

A

9.8m/s2
32.2ft/s2
(considered constant but not truly)

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10
Q

For this class, pounds (lb) refers to ___ where as slugs refers to ___.

A

force [=] lb (pound force)

mass [=] slugs

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11
Q

Mass is:

A
  1. scalar quantity
  2. Amount of material in a body
  3. measure of inertia (measure of resistance to change)
  4. same in any gravitational field (independent of location)
  5. [=] slugs, kg (1 slug = 14.59 kg)
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12
Q

Weight is:

A
  1. Vector quantity
  2. Effect of gravity on a body
  3. measure of Force (exerted on a body by a gravitational field)
  4. varies with strength of g (dependent on location)
  5. [=] lb, N (1 lb = 4.448 N)
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13
Q

What is a rigid body?

A

a model of a material body or system of particles in which the distence between any two particles remains the same (ie. no deformation)

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14
Q

What is a scalar? Give examples.

A

a physical quantity that has magnitude only (can be specified without mentioning direction)
(eg. time, temperature, volume, mass, distance, speed)

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15
Q

What is a vector? Give examples.

A

a mathematical quantity (directed line segment) completely specified by mentioning magnitude, direction, and which adds according to the Parallelogram Rule
(eg. Displacement, position, velocity, acceleration, momentum, or force)

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16
Q

What is the magnitude of a vector?

A

its length

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17
Q

What are the 3 types of vectors?

A
  • Free
  • Sliding
  • Bound
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18
Q

What is a free vector?

A

Has definite magnitude and direction but NO specific location in space
(eg. moment vector of a couple)

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19
Q

What is a sliding vector?

A

can be moved along a given line collinear with the vector’s line of action
(eg. force acting on a rotating rigid body)

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20
Q

What is a bound vector?

A

has a specified point of application (aka. fixed vector)

eg. a force acting on a deformable body

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21
Q

What are two vector quantities dealt with extensively in Statics?

A

Force and momentum

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22
Q

What is a force?

A
  • a quantity which tends to change the state of motion of a body
  • the action of one body on another
  • (felt as a push or pull)
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23
Q

A force is characterized by:

A
  1. point of application
  2. its magnitude
  3. its direction (defined by the line of action {infinite straight line along which the force acts} and the sense {direction} of the force)
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24
Q

What are some ways forces can be classified?

A
  1. Concentrated force (load)
  2. Distributed load
  3. External forces
  4. Internal forces
  5. Collinear forces
  6. Coplanar forces
  7. Concurrent forces
  8. General space force systems
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25
Q

What is a concentrated load?

A

a force representing the effect of loading which is assumed to act at a point on a body

26
Q

What is a distributed load

A

a force or force system spread over an area.

27
Q

What are the two types of distributed load?

A

Uniform

Non-uniform

28
Q

What is an external load?

A

a force acting on the outside of a structure set in equlibrium

29
Q

What is an internal load?

A

a force effect within the entity or any component part of a structure set in equilibrium

30
Q

Are internal effects altered by loading substitutions?

A

yes

31
Q

Are external reactions altered by the application of a load to any point along its line of action?

A

No

32
Q

What are the ways forces/ force systems can be classified according to the arrangement of their lines of action?

A
  1. Collinear forces
  2. Coplanar forces
  3. Concurrent forces
  4. General space force systems
33
Q

What are coplanar forces?

A

forces that all lie in the same plane

34
Q

What are concurrent forces?

A

forces that all intersect at a common point

35
Q

What is a general space force system

A

A force system that is non-coplanar, non-parallel, non-concurrent, non-collinear

36
Q

What is a Free-Body Diagram (FBD)?

A

a diagram of a body (or group of bodies, or part of a body) which is isolated from its environment and on which all external forces are applied

  • FBD = “F’n Big Deal”
  • first step in dealing with any problem in mechanics
37
Q

What is a moment (M)?

A

provides a measure of the tendency of a force to cause an object to rotate (about a point or axis)
M = Fd (scalar)
M = r x F (vector)
- M: moment
- F: force creating M
- d: perpendicular distance from line of action of the force to the moment center
- r: position vector form moment center to force

38
Q

What are the 12 concepts of statics?

A
  1. Force
  2. Parallelogram Rule
    * 3. Equilibrium
  3. Moment
  4. Varignon’s Theorem
    * 6. Equivalence
  5. Transmissibility
  6. Lateral Transfer Theorem
  7. Newton’s 3rd Law
  8. Superposition
  9. Friction
  10. Area moment of Inertia (I)
39
Q

What is the concept of Equivalence?

A

All systems can be reduced to a single force and moment (in special situations to a single force at a know location)

40
Q

What is the concept of Force?

A

has magnitude, direction and line of action (push or pull)

41
Q

What is the concept of Parallelogram Rule?

A

law of vector addition. Added by placing vectors head to tail to form a parallelogram
(Triangle construction only uses half of parallelogram)

42
Q

What is the concept of Equilibrium?

A

Sum of forces = 0 (particle) and sum F = 0, sum M = 0 (rigid body)
(#1 concept!)

43
Q

What is the concept of Moment?

A

tendency of a force to cause rotation about a point or axis (M=r x F) or (M=Fd)

44
Q

What is the concept of Varignon’s Theorem?

A

You can use the force or the component of the force to calculate the moment

45
Q

What is the concept of Equivalence?

A

All systems can be reduced to a single force and moment (in special situations to a single force at a know location)
(important!)

46
Q

What are four types of forces?

A
  1. Body force
  2. Surface/Contact force
  3. Concentrated force
  4. Distributed force
47
Q

What is a Body force?

A

a force due to the attraction between two bodies (no physical contact)

48
Q

What are four types of forces?

A
  1. Body force
  2. Surface/Contact force
  3. Concentrated force
  4. Distributed force
49
Q

What is a Surface/Contact force?

A

force between two bodied due to the contact between them

50
Q

What is a Concentrated force?

A

a force acting at a particular point, not over an area

51
Q

What is a Distributed force?

A

a force spread over an area

52
Q

Six force systems used in statics are?

A
  1. Coplanar, parallel
  2. Coplanar. concurrent
  3. Coplanar, non-concurrent
  4. Non-coplanar, parallel
  5. Non-coplanar. concurrent
  6. Non-coplanar, non-concurrent
53
Q

What is a Resultant?

A

a force which is the vector sum of all forces acting on a body and which has the same net external effect as the original force system

54
Q

What is Resolution of a force?

A

the replacement of a single force with two forces acting along a set of particular axes

55
Q

What is Resolution of a force?

A

the replacement of a single force with two forces acting along a set of particular axes

56
Q

What is the coordinate direction angle?

A

In 3-D, the angle between the tail of a vector and the coordinate axes

  • alpha = angle from the x-axis to the tail of the vector
  • beta = angle from the y-axis to the tail of the vector
  • gamma = angle from the z-axis to the tail of the vector
57
Q

What are the Coordinate Direction Cosines?

A

The cosine of the angel between a vector and a coordinate axis (ie. the cosine of alpha, beta, and gamma)
- direction of cosine is equal to the ratio of the orthogonal scalar component of a vector to the magnitude of a vector

58
Q

What is the identity involving the Coordinate Direction Cosines?

A

cos^2(alpha) + cos^2(beta) + cos^2(gamma) = 1

59
Q

What is the position vector?

A

a fixed vector which locates a point in space relative (ie. a difference) to another point

60
Q

How do you find the position vector?

A

Take the coordinates of the tip of the vector and subtract the corresponding coordinates of the tail.

61
Q

What are the Coordinate Direction Cosines?

A

The cosine of the angel between a vector and a coordinate axis (ie. the cosine of alpha, beta, and gamma)
- direction of cosine is equal to the ratio of the orthogonal scalar component of a vector to the magnitude of a vector
cos(alpha) = Fx/F
cos(beta) = Fy/F
cos(gamma) = Fz/F

62
Q

What is the identity involving the Coordinate Direction Cosines?

A

cos^2(alpha) + cos^2(beta) + cos^2(gamma) = 1

*statics (4 decks)

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