Intro to Biomechanics Flashcards
newtons first law
An object will remain at rest or in some uniform motion in a straight line unless some net external force acts upon it.
inertia
This tendency to remain in its current state
force is ..
vector quantity.
The total or ___ acting on an object is the ___acting on the object.
The total or net force acting on an object is the vector sum of all the forces acting on the object.
newtons second law
The acceleration (a) of an object is directly proportional to the net external force (F) exerted on it, and inversely proportional to its mass (m)
newtons second law equation
F = ma m = mass F= External force a = acceleration
kinematics
study of motions
statics
mechanics of fixed systems
units of forces
are kg m s-2 or Newton (N).
mechanics is essential to understand
Joint articulation Stability and balance Structure and function of bones Weight and effective weight Effect of impulse and impact Effect of motion and acceleration
An important force in biomechanics is the ___
An important force in biomechanics is the gravitational force or weight
why is weight calculated by mass x acceleration
Since the acceleration due to gravity (g) acts vertically downward, the gravitational force or weight (W) on an object of mass (m) is given by mass x acceleration,
weight formula
m(mass) x g(gravity)
newtons third law
If an object exerts a force (F) on a second object, then the second object exerts an equal in magnitude, but opposite in direction force (-F) on the first object.
acceleration
change of velocity
quantity vector
direction and magnitude
the ability for the body to withstand large accelerations is dependant on what
on magnitude and duration of acceleration
why is the ability to withstand large acceleration dependant on its duration and magnitude
This is due mainly to the structural strength of the bone structures, as well as the inertia of the blood and internal organs
inertia
can displace organs when large acceleration
examples of physiological effects from large acceleration
heart struggles to pump blood w/ effective weight
reduced blood pressure in retina
sensitive to O2 deprivation - possible blackout
reduced blood pressure in brain - possible unconsciousness
momentum
mass x velocity
vector quantity
units of momentum
kg m s-1
principle of conservation of linear momentum
‘If there is no external force applied to a system then the total linear momentum of that system remains constant in time
momentum = mass x velocity
if there is a change in velocity there is a force applied
If there is a change of momentum there will be impact force
change in velocity means
force is applied
impulse Ft
acceleration = (v2 - v1)/t
newtons second law F =ma
F = m(v2-v1)/t
Ft = m(v2-v1)/t
how can the impact force of a car accident be reduced
impulse is fixed by the initial speed to 0(the collision)
impact force can be reduced by increasing the time over which the momentum changes
how do we try to minimise impact force by increasing the time over the impact occurs
seat belt tightens after speed increases
reduce impact force
air bags -collision with it come to a stop/rest over a longer period of time than when it hits a windscreen
crumple zone - infront and back of cars which design to collapse on impact - increase the time in which car comes to rest
reduce speed - lower change in velocity
whiplash
physical damage to the upper spinal column or muscles in the neck region due to inertia of the body resulting from an impact from either the front or rear.
energy
The ability to do work
conservaton of energy
Within a closed system, the total amount of energy is constant.
energy is measured in
joules
work
Work Done (W) on a body by a force (F) in moving the object through a distance (d) is given by
work formula
W = F x d
impulse
change of momentum
work is a …
vector quantity
how else can work be calculated
distance moved in DIRECTION in which the force is applied
work done = Fcos0 x distance moved
work can also be defined as
expenditure of energy
e.g. pushing against a wall or carrying a load in a stationary position still constitutes as work
kinetic energy
energy due to an objects motion
= 1/2mv^2
m =mass
v= velocity
potential energy
energy an object has due to its shape or position mgh m =mass g = gravity h = height
work energy principle
The total Mechanical Energy of a system is the sum of the Kinetic and Potential energies.
Total Mechanical Energy of a system at some time is EQUAL to the Total Mechanical Energy of the system at some later time +/- any Work Done on/by the system,
an example of chemical energy important in our physiology
calorific energy associated with food
metabolism
Normal bodily activity requires work to be expended
BMR
1.22kCal/minute
how many calories used a day
1750kCal/day
power calculation
work done/time
power definition
the rate at which energy is expended and is defined as follows:
efficiency
the ratio of the work done on the required activity to the TOTAL energy expended
efficiency
the ratio of the work done on the required activity to the TOTAL energy expended
