731 Mechanics Introduction

biomechanics

the study of movement of living structures

kinematics

motion of the body

translation (linear motion)

motion in which all parts of a rigid body move parallel to and in the same direction as every other body part. Measured in meters or feet

rectilinear

movement occurs in a straight line

curvilinear

movement occurs in a curved line

rotation (angular motion)

Motion in which an assumed rigid body moves in a circular path about some pivot point or axis of rotation. All points in the body simultaneously rotate in the same angular directin across the same angular displacement.

kinetics

branch of mechanics that studies the effect of forces on the body

force

a push or a pull

internal force

produced from structures within the body. These may be active like stimulated muscle, or passive such as tissues stretched in tension

external forces

produced from forces acting outside the body. Ex. gravity, external load like a dumbbell, physical contact from another person

joint reaction force

another type of internal force resulting of contact forces between the articulating bones in a joint

torques

forces applied some perpendicular distance away from the axis of rotation. The rotary or turning effect of a force. Torque = Force * Moment Arm

moment arm (D)

the perpendicular distance from the applied force to the axis of rotation

Define mechanics, biomechanics, kinematics, kinetics, and associated terms.

Mechanics—> the branch of physics that deals with motion of objects and the forces acting on them

biomechanics—>the study of movement of living structures

kinematics—>motion of the body

Kinetics—>branch of mechanics that studies the effect of forces on the body

Distinguish between internal and external forces acting on a body.

Internal forces are forces that parts of a body exert on each other; they act within the system and do not change the body’s overall motion, only its internal shape or stress. External forces come from outside the body (like gravity, friction, or applied pushes) and can change its motion, acceleration, or overall equilibrium.

Describe the relationship between force, moment arm, and torque.

A force (a push or a pull) is applied which creates a moment arm perpendicular to where the force is applied and the axis of rotation. This force will then create rotary or turning effect on force such as torque allowing the object either internal or external to move.