intro to biomechanics

Question 1

what is kinematics?

Answer 1

the study of motion

Question 2

what is statics?

Answer 2

the mechanics of fixed systems

Question 3

why is mechanics essential to understand for physio?

Answer 3

-joint articulation
-stability and balance
-structure & function of bones
- weight
-effect of impulse and impact
-effect pod motion and acceleration

Question 4

what is inertia?

Answer 4

-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

Question 5

what is acceleration?

Answer 5

the rate at which something speeds up, slows down or changes direction

Question 6

what is a reaction force ?

Answer 6

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

Question 7

what is impulse and impact?

Answer 7

-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

Question 8

what is momentum?

Answer 8

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

Question 9

what is force in physics?

Answer 9

-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

Question 10

describe newtons first law of motion- law of inertia

Answer 10

-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

Question 11

describe newton’s 2nd law of motion

Answer 11

-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

Question 12

what is the important formula for newtons 2nd law of motion - related to force, acceleration & mass?

Answer 12

F= ma

Question 13

describe newtons 3rd law of motion

Answer 13

-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

Question 14

what is ground reaction force?

Answer 14

-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

Question 15

what happens to blood in the body when the human body is accelerated upwards?

Answer 15

the blood accumulates in the lower body

Question 16

what happens to blood in human body when it has accelerated downwards ?

Answer 16

-blood accumulates in the upper body

Question 17

what is real weight?

Answer 17

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

Question 18

what is effective weight & give an example scenario?

Answer 18

-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

Question 19

what is the limit of tolerance of acceleration?

Answer 19

• 10g

Question 20

what is the equation for momentum & what are its units?

Answer 20

M= mass x velocity
-units - kg ms-1

Question 21

what does Ft stand for?

Answer 21

impulse

Question 22

what is the impulse formula?

Answer 22

-Ft= m(V2-V1)

Ft= impulse
t= time over which the momentum changes
V2-V1- change in acceleration

Question 23

how are impact forces relevant to physiotherapy?

Answer 23

-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

Question 24

how can the impact force be minimised in a RTA collision?

Answer 24

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

Question 25

what is whiplash?

Answer 25

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

Question 26

what is energy in physics?

Answer 26

the ability to do work
-comes in various forms and can be transformed from one form to another eg kinetic, potential, thermal energy

Question 27

what is the law of conservation of energy?

Answer 27

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

Question 28

what is work??

Answer 28

• 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)

Question 29

how is work defined as the expenditure of energy?

Answer 29

-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

Question 30

what is kinetic energy?

Answer 30

• kinetic energy is the energy of motion - ie when something is moving it has kinetic energy

Question 31

what is the formula for kinetic energy?

Answer 31

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

Question 32

what is potential energy & give an example ?

Answer 32

-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

Question 33

what is the total mechanical energy os a system the sum of?

Answer 33

the sum of the kinetic and potential energies

Question 34

what is the work-energy principle?

Answer 34

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.

Question 35

what is the form of chemical energy associated with food?

Answer 35

calorific energy

Question 36

what is the BMR?

Answer 36

the energy conversion rate of a person at rest, and is responsible for minimal bodily function

Question 37

what is power defined as?

Answer 37

the rate at which energy is expended / the rate at which work is done

power = work done/ time

Question 38

what are the units of power?

Answer 38

joules/sec or watts

Question 39

what is the efficiency of an device in physics?

Answer 39

• the more efficient a device is, the more useful work it can do for a given energy input

Question 40

if no movement occurs under muscle tendon (ie isometric contraction) is any mechanical work done?

Answer 40

-yes because the muscles are under tension and they shorten and contract, so work energy is expended