Force, Torque, Equilibrium

kinematics

the motion of the body without consideration of forces

kinetics

division of mechanics describing the effects of forces on the body

a push or a pull

F=ma

what is a force, what is its formula

an object at rest will stay at rest and an object at motion will stay in motion unless acted on by another force

what is newtons 1st law

F=ma, acceleration is proportional to force

what is newtons second law

every action has an equal and opposite reaction

what is newtons 3rd law

vectors

forces are represented by...

direction and magnitude

vectors have...

by adding the vectors using tip to tail and connecting them to make a resultant vector

multiple forces act on the body at the same time, how are they added

SOH

CAH

TOA

how are components of a vector found

draw a free body diagram

turn vectors into vertical and horizontal components

add the vertical and horizontal components separately

use the pythagorean theorem if needed

what are the steps of vector addition?

direction

when adding vectors it is important to consider...

rigid bodies and do not deform

for motion analysis, we assume that tissues are...

translation and rotation

what can forces do to rigid bodies

internal forces and external forces

what types of forces move rigid bodies

at the center of pressure

where does the ground reaction force act on the rigid body

at the insertion and origin of the muscle

where do internal forces act on the rigid body

point of application, center of mass, center of pressure

where to external forces act on the rigid body

moment arm

the distance of the force to the center of rotation is called the...

they all are equal to 0

when the rigid body is in equilibrium what does that say about the forces and torque

translation

the sum of the the forces will give us...

rotation

the sum of the torques will give us..

an axis of rotation

what is needed for torque

at some point perpendicular to the axis of rotation

where is the force applied for torque

counterclockwise

in what direction is torque positive

clockwise

in what direction is torque negative

the right hand rule

how do we find the direction of torque

F*moment arm

what is the formula for torque

perpendicular

force and moment arm need to be...

adding up all the torques

how is the total torque on a system calculated

mechanical advantage

having a larger moment arm is referred to as having

rotation moment (normal force)

joint compression (tangential force)

force of a muscle can be split into 2 component's, what are they

rotation moment: Y component of the force

joint compression: X component

what part of the force is the rotation moment and joint compression correspond to?

internal forces are multiplied by the internal moment arm

to find internal torque...

leverage

forces with shorter moment arms have less...

having a longer lever arm allows the same production of force with less effort

how do moment arms relate to MMT?

closer to the body

internal torque can become smaller when the force is...

find the direction of the torque using the RHR

before finding torque on a system, what should be done?

isolate the free body being analyzed

establish coordinates

draw internal and external forces

find joint reaction force

what is the process of solving torque equations

only the rotational moment of the force (Fy) is used

when solving for torque of the muscle, what component is used as force

the axis of rotation is between opposing forces

what is a first class lever

internal force has more leverage (longer lever arm, further from the axis) than the external force on the same side of the axis

what is a second class lever

external force has more leverage (longer lever arm, further from the axis) than the internal force on the same side of the axis

what is a third class lever?