intro to biomechanics Flashcards
what is kinematics?
the study of motion
what is statics?
the mechanics of fixed systems
why is mechanics essential to understand for physio?
-joint articulation
-stability and balance
-structure & function of bones
- weight
-effect of impulse and impact
-effect pod motion and acceleration
what is inertia?
-describes that objects like to keep doing what they’re already doing
-ie if somethings moving, it wants to keep moving in the same way unless something interferes
-if something is not moving, it tends to stay still unless you push or pull it
what is acceleration?
the rate at which something speeds up, slows down or changes direction
what is a reaction force ?
the force exerted by an object in response to a force applied to it - newtons third law of motion
-eg pushing against a wall, the wall exerts a reaction force back on your
what is impulse and impact?
-impulse - the measure of the change in momentum of an object when a force is applied to it for a certain amount of time
-impact - contact between 2 objects - transfer of momentum and energy between objects involved in the collision and involves changes in velocities and directions of objects
what is momentum?
describes the motion of an object - how much ‘oomph’ it has when its moving
-it is defined as the product of an objects mass & its velocity
what is force in physics?
-a vector quantity - meaning it has both magnitude (size and length) and direction
-describes an interaction that can change the state of motion or shape of an object eg force can cause an object to accelerate, decelerate or change direction or deform
describe newtons first law of motion- law of inertia
-an object will remain at rest, or continue to move at a constant velocity in a straight line, unless acted upon by a net external force
describe newton’s 2nd law of motion
-the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass
-F = ma
-eg a small force will cause a small acceleration on a heavy object, while the same force will cause a larger acceleration on a lighter object
what is the important formula for newtons 2nd law of motion - related to force, acceleration & mass?
F= ma
describe newtons 3rd law of motion
-for every action, there is an equal an opposite reaction
- if object A pushes on object B, object B pushes back on object A with the same force but in the opposite direction
what is ground reaction force?
-the force exerted by the ground on an object in contact with it, such as a persons foot
-when you walk agains the ground, it pushes back with an equal and opposite force
what happens to blood in the body when the human body is accelerated upwards?
the blood accumulates in the lower body
what happens to blood in human body when it has accelerated downwards ?
-blood accumulates in the upper body
what is real weight?
the actual force of gravity pulling on an object due to its mass
-it is what you would measure if you placed an object on a scale
what is effective weight & give an example scenario?
-effectuve weight is different to real weight, as it takes into account other forces that may be acting on the object in addition to gravity
-eg when in an elevator going up, you might feel heavier because the elevator floor is pushing you up in addition to gravity… ie your effective weight would be the combination of force due to gravity & force due to lifts acceleration
what is the limit of tolerance of acceleration?
- 10g
what is the equation for momentum & what are its units?
M= mass x velocity
-units - kg ms-1
what does Ft stand for?
impulse
what is the impulse formula?
-Ft= m(V2-V1)
Ft= impulse
t= time over which the momentum changes
V2-V1- change in acceleration
how are impact forces relevant to physiotherapy?
-impact forces can occur in various contexts and they affect different parts of body and may play a role in injury prevention, rehab and performance enhancement
-eg gait analysis - analysing the impact forces during walking or running can help physios to understand how forces are transmitted to the lower limbs and also to assess gait abnormalities
how can the impact force be minimised in a RTA collision?
the time over which the impact occurs should be as long as possible
- wear a seatbelt
-airbags - driver will come to rest much slower
-crumple zones - structures @ back & front of car which are designed to collapse on impact - increase the time it takes for the car to come to rest
-reduce speed
what is whiplash?
physical damage to the upper spinal column or muscles in the neck region due to inertia of the body from an impact from either the front or rear
what is energy in physics?
the ability to do work
-comes in various forms and can be transformed from one form to another eg kinetic, potential, thermal energy
what is the law of conservation of energy?
the total energy of an isolated system remains constant over time
-energy cannot be created nor destroyed, it can only change forms or be transferred from one object or system to another
what is work??
- work is when you use a force to move something over a distance
-eg if you push or pull something and it moves you’ve done work on it - W= F x d (where F = force and d= distance)
how is work defined as the expenditure of energy?
-if an object does work, it expends or looses some or all of its energy
-if work is done on an object, it gains the equivalent amount of energy
what is kinetic energy?
- kinetic energy is the energy of motion - ie when something is moving it has kinetic energy
what is the formula for kinetic energy?
KE= 1/2 mv^2
-KE= kinetic energy
m= mass of object
v= velocity (speed) of object
ie if something is heavy and moving fast, it has a lot of kinetic energy, but if its light and moving slowly, it has less kinetic energy
what is potential energy & give an example ?
-Potential energy is the energy stored in an object due to its position or condition. It’s like having energy waiting to be used
- egImagine holding a ball high above the ground. Because of its position above the ground, the ball has potential energy. If you let go of the ball, it will fall due to gravity, and its potential energy will be converted into kinetic energy
what is the total mechanical energy os a system the sum of?
the sum of the kinetic and potential energies
what is the work-energy principle?
the work done on an object is equal to the change in its kinetic energy. In simpler terms, when you do work on an object, you’re giving it energy, and that energy can make the object move faster or slower.
what is the form of chemical energy associated with food?
calorific energy
what is the BMR?
the energy conversion rate of a person at rest, and is responsible for minimal bodily function
what is power defined as?
the rate at which energy is expended / the rate at which work is done
power = work done/ time
what are the units of power?
joules/sec or watts
what is the efficiency of an device in physics?
- the more efficient a device is, the more useful work it can do for a given energy input
if no movement occurs under muscle tendon (ie isometric contraction) is any mechanical work done?
-yes because the muscles are under tension and they shorten and contract, so work energy is expended
