Topic 5 ( EQUILIBRIUM OF A RIGID BODY )

Question 1

Keywords: Zero forces, zero moments, balance
Definition: A rigid body is in equilibrium when the resultant forces and resultant moments acting on it are zero.

Answer 1

Equilibrium

Question 2

ΣFx = 0, ΣFy = 0, ΣM = 0

Answer 2

Equilibrium Conditions

Question 2

Keywords: External, known forces
Definition: Forces exerted on a body by external agents, such as weights, wind, or tension in a cable.

Answer 2

Applied Forces

Question 3

Keywords: Support, resistance, unknown forces
Definition: Forces exerted by supports or connections to resist motion. Examples include normal forces, tension, and friction.

Answer 3

Reactive Force

Question 4

Types of Supports

Answer 4

Pin, roller, fixed, reaction types

Question 5

Restricts movement in two directions (horizontal and vertical forces).

Answer 5

Pin Support:

Question 6

Restricts movement in one direction (vertical or horizontal force only).

Answer 6

Roller Support

Question 7

Restricts all movement and rotation (horizontal, vertical, and moment reactions).

Answer 7

Fixed Support

Question 8

Rotation, force × distance

Answer 8

Moment

Question 9

Keywords: Solvable, equations = unknowns
Definition: A structure or system where the number of equilibrium equations equals the number of unknowns, allowing it to be solved using only equilibrium conditions.

Answer 9

Statically Determinate

Question 10

Keywords: Excess unknowns, requires other methods
Definition: A structure or system where the number of unknowns exceeds the equilibrium equations, requiring additional methods (e.g., compatibility equations).

Answer 10

Statically Indeterminate

Question 11

Keywords: 2D, coplanar forces
Definition: The geometric plane in which all forces acting on a body lie.

Answer 11

Plane of Action

Question 12

Keywords: Coplanar, concurrent, parallel
Definition: A group of forces acting on a rigid body, categorized as concurrent, parallel, or non-concurrent/non-parallel.

Answer 12

Force System

Question 13

is a simplified representation of an object or system, showing all the forces acting on it. It’s a critical tool in mechanics, especially in statics and dynamics, to analyze and solve problems involving forces and moments.

Answer 13

Free Body Diagram (FBD)

Question 14

An _____ is any external force exerted on an object by another object, person, or system. It’s what initiates motion, deformation, or some other effect.
eX. Pushing a box across the floor.
A person pulling on a rope.
The thrust from an engine.

Answer 14

applied force

Question 15

A ____ is a force that opposes or reacts to an applied force, according to Newton’s Third Law (“For every action, there is an equal and opposite reaction”).
Ex. A table exerting an upward force on a book placed on it (normal force).
The ground pushing back when you step on it.
The tension in a rope countering the pull of gravity.

Answer 15

reactive force

Question 16

Examples of ____ include normal force, friction, and tension.

Answer 16

reactive forces

Question 17

_____ Force comes from an external agent

Answer 17

Applied

Question 18

___ Force originates due to the response of the object or environment to the applied force.
also acts in the opposite direction of the applied force.

Answer 18

Reactive

Question 19

_____can only support tensile forces (pulling forces). It cannot resist compressive or bending forces.

Answer 19

flexible cable

Question 20

____ are often used in problems involving pulleys, hanging loads, suspension bridges, or hoisting systems.

Answer 20

cables

Question 21

A ___ support is a type of support used in engineering to allow a structure to rest on it while permitting movement in one direction, typically horizontal. It is commonly used in problems involving beams or structures that need flexibility to move or expand due to thermal effects, wind loads, or other factors.

Answer 21

roller

Question 22

A ___ support only provides one reaction force. This force is perpendicular to the surface the roller rests on (usually vertical), but it does not resist horizontal movement.

Answer 22

roller

Question 23

The__supports the structure vertically, but it does not prevent it from moving sideways (in the horizontal direction).

Answer 23

roller

Question 24

A____support is often represented by a circle with a perpendicular arrow pointing upward to indicate the vertical reaction force.

Answer 24

roller