types of machines in the body

Question 1

ITT-
how forces are applied and motion produced
(centric, eccentric, force couple)

Answer 1

c- ext force directed through objects centre of gravity causing linear motion
e- ext force not directed through objects centre of gravity causing linear and angular motion
fc- forces equal in size, opposite direction but not on same line causing angular motion

Question 2

ITT-
torque
(what is it, calc, what is moment arm and implications of diff lengths, - and + torques)

Answer 2

rotatory force when line of action of force doesn’t pass through axis of rotation
torque (NM) = force x moment arm
the perpendicular distance between the line of action and a parallel line passing through objects axis of rotation
with same force, longer moment arm= greater torque, eg. why we use a spanner
counter clockwise rotation positive, clockwise rotation negative

Question 3

levers-
components and functions in body

Answer 3

joint is axis of rotation
effort force produced by muscles
resistance forces which are counteracted (eg. weight external pushes)
lever arm (bone)
used to generate torques onto joints to rotate our limbs

Question 4

levers-
mechanical advantage
(what they gain, calc, impact of length of FA, type in body)

Answer 4

-mechanical advantage increases force applied onto an object
- mechanical advantage= length of FA (distance from force to axis of rotation) / length of RA (distance from resistance to axis of rotation)
- FA>RA = MA>1 so small movement at 1 point gives large movement at another, eg. shovel
- RA>FA = MA<1 so less torque, more force has to be produced to counteract resistance
- body mostly this/3rd class lever

Question 5

levers-
how to remember

Answer 5

FLE
123

Question 6

levers-
1st class
(mechanical advantage, eg.)

Answer 6

high/low MA depending on length of FA and RA
eg. nodding head on neck

Question 7

levers-
2nd class
(MA, eg.)

Answer 7

FA>RA so MA greater increasing torque so have high mechanical advantage above 1 (strong and forceful)
+ are rare in body
eg. plantar flexion so standing uses little energy

Question 8

levers-
3rd class
(MA, eg.)

Answer 8

small resistance generate large torque as RA>FA so large muscle force generated to counteract resistance torques, as mechanical advantage below 1
+ most common in body
eg. elbow flexion

Question 9

levers-
benefits of third-class levers

Answer 9

• designed for speed and ROM
• when muscle contacts the resistance moves a greater displacement (greater velocity), eg. bicep curl

Question 10

static equilibrium-
torques and static equilibrium
(what is required for static equlibrium, SE equation for torque, what contractions are in SE)

Answer 10

• both external force and external torques must = 0
• sum of torque = (Fa x Ra) + (Fb x Rb) = 0

Question 11

static equilibrium-
how does net force = 0 when resistance and effort force are different

Answer 11

joint reaction force that is equal and opposite to force of muscle-resistance force
acts directly on the axis/joint so MA = 0 so torque = 0 and remains balanced

Question 12

static equilibrium-
impact of moment arm changing when joint angle changing

Answer 12

• at 90 deg MA longest so muscle is strongest
• if MA decreases, muscle is required to generate more force for the same torque.