centre of gravity and balance

Question 1

define the centre of gravity

Answer 1

it is the single point where all the mass of the object is imagined to be

Question 2

where is the COG located for uniformly dense and symmetric objects?

Answer 2

-located at their geometric centres

Question 3

for non-uniformly dense or non-symmetric objects, where is the COG located?

Answer 3

-can be off centre or even located outside of the object

Question 4

how much % wise do the upper legs of a typical human take up of the total body mass?

Answer 4

19.3%

Question 5

where is the COG of a suspended hanging obeject?

Answer 5

COG is directly below the point of suspension ( what ever is hanging the object up)

Question 6

if the COG is centred between 2 supports, what happens to the torques and reaction forces?,

Answer 6

the torques about the COG due to the reaction forces R1 & R2 are opposite and equal and cancel each other out
-ie net force and net torque are equal to 0 so the beam is in equilibrium and ‘balanced’

Question 7

if the COG is to the left of the same 2 supports, what happens to the torques?

Answer 7

the torques about the COG are both in the same direction and the net torque is not equal to 0 (remember net torque and force must equal 0 for something to be in equilibrium)
-the beam then becomes unstable and topples over

Question 8

take a table with shorter vs longer legs and compare the COG and stability

Answer 8

• the table with the shorter legs has a larger angle at which the COG lies within the base of support = greater stability

Question 9

does a higher or lower COG give greater stability?

Answer 9

lower

Question 10

what happens to our COG when we move?

Answer 10

our COG also moves too

Question 11

what are examples of stable activity and where does the COG lie during these activities?

Answer 11

-examples: walking, standing or leaning
-COG lies within the area of support

Question 12

what are examples of unstable activity and where does the COG lie?

Answer 12

-activities where the COG lies outside of the area of support, leading to loss of balance & potential falls
-eg leaning too far forward or backward

Question 13

what happens to the cog when you lift a patient?

Answer 13

-centre of gravity of both you (HCP) and patient are combined and shifts
-maintaining balance and stability is crucial to prevent falls and injuries

Question 14

what are the implications of the change of COG when lifting a patient?

Answer 14

relate to the safety and stability of the HCP lifting and the patient being lifted

Question 15

why do back problems occur in pregnant women (relate to COG)?

Answer 15

back problems can happen due to a significant forward shift in their COG
-this can create large torques which causes excess stress on the spine and lower back muscles

Question 16

why can poor posture lead to long term problems if not corrected (relate to COG)?

Answer 16

• can shift COG - which places stress on muscles bones and joints & ligaments of spine
  -if COG is not in proper alignment, it can be harder to have more balance and stability, this may increase the risk for falls and injuries

Question 17

what happens to the COG of an amputee and what effect does this have on their stability?

Answer 17

-amputation of a limb esp a lower limb can cause the COG to shift - towards the amputated limb which can cause issues with balance and stability
- altered base of support - become narrower which further comprimises stability