Mechanics: Statics, Dynamics, and Motion Analysis
Statics and Dynamics
Statics is the area of mechanics that studies bodies at rest or in equilibrium as a result of forces acting on them. Dynamics is the area of mechanics that studies bodies in motion.
Kinematics and Kinetics
Kinematics is the study of the relationships between the displacements, velocities, and accelerations in translational or rotational motion. Kinetics studies bodies in motion and the forces acting to produce them.
Force
A force is a push or pull on a body. To produce a force, one body must always act upon another.
- External forces: Gravity, resistance, water, air, inertia, and so on.
- Internal forces: Internal resistance of a material that reacts to an externally applied load.
Force Characteristics
- Magnitude: A scalar quantity (F or P if the magnitude of force is not known).
- Action Line: A line of force application.
- Direction: The sense of application of force.
- Point of application: The point at which the force is applied.
Scalar and Vector Quantities
A scalar is a quantity of magnitude. A vector is a quantity that has a direction, represented by a directed straight line, its length should be proportional to the force.
Force System
A force system is any group of two or more forces.
Subject Matter, Mass, and Weight
Subject matter is all that occupies a place in space. The amount of matter is called mass. Weight is the pull of gravity on mass.
Pressure
Pressure is the ratio of total force and its relation to the area of application.
Diagrams and Reference Systems
A diagram space is a simplified drawing representative of the body, constituted to identify the forces and moments acting on individual parts of a system. A free body diagram has forces drawn in correct proportion. A reference system allows us to make special calculations that determine changes in position or displacement generated by the body or its segments.
Center of Mass and Center of Gravity
Center of mass means the point at which exactly is the center of mass, also known as the center of gravity.
- Mass in symmetry is at the geometric center of the body.
- Mass in asymmetry is near the larger and heavier end.
Laws of Motion
- Law of inertia: Every body remains at rest or in uniform motion until external forces act on it.
- Law of acceleration: The acceleration of a particle is directly proportional to the unbalanced force acting on it and inversely proportional to the mass of the particle.
- Action-reaction: For every action, there is an equal and opposite reaction.
Movement Classification
Movement can be classified:
a) Depending on the type of path described by the particle.
b) Depending on the type of speed.
- Linear movement: When all the particles of a mobile describe parallel trajectories along a movement.
- Straight linear movement: For the movement, one or a few segments remain always parallel to that used initially.
- Curvilinear linear movement: A curvilinear translation movement involves a curved path and parallel segments or moving particles.
- Angular movement: It implies that all particles of a mobile describe the same displacement angle while moving to complete the necessary rotation axis.
- Widespread movement: It corresponds to the combination of linear and angular movement.
According to the speed:
- Uniform movement: Displacement corresponds to a constant speed maintained over time.
- Variable movement: Implies that the rate does not remain constant and can be increased or decreased.
Movement Manifestations
- Global forms: They are full and natural in humans.
- Basic shapes: Walking, running, jumping, throwing, and so on.
- Skills: Jumping improved through training, and so on.
- Built: Man-made.
- Analytical: Referring to a part, the body segment moves while the rest stays still.
- Analytical summary: The combination of analytical exercises (muscle groups movement) to other fixed ones.
- Synthetics: These are wide movements with full participation of the muscle groups that move in space in multiple directions.
- Repetitions: Referring to the repeated action of sports technique, cyclic and acyclic.
- Coping: Refers to the solution of problems and decisions, open and closed.
Center of Mass and Center of Gravity (Revisited)
Center of mass means that point in a material body that moves as if the total mass of the system is at that point and all external forces were applied to it. The center of gravity is defined as a fixed point of a material body where the resulting gravitational force acts.
Lever
A lever is a simple machine that is designed to balance or move a force (resistance) through another force (power), improving the application of power.
Force System (Revisited)
A force system is a set of forces acting simultaneously on the same body. Each of the forces acting is called a component of the system.