Balance

Question 1

What is does it mean for something to be stable?

Answer 1

The forces acting upon an object are equal to the forces the object is acting upon its surroundings?

Question 2

What is a stable equilibrium?

Answer 2

Occurs when a disturbance to an object / person will only cause it to gain stability again?

Question 3

What is an unstable equilibrium?

Answer 3

It means that when a force is applied to a person or object, it will need to find a new position?

Question 4

What is neutral equilibrium?

Answer 4

When an object will move but remain perfectly stable?

Question 5

What is the center of gravity?

Answer 5

• Aka “COG” or Center of mass (COM)
• The theoretical point around which the mass of the point is balance

Question 6

Does the center of gravity need to be inside of an object / person?

Answer 6

No

Question 7

Where is the center of gravity in humans?

Answer 7

• An inch below the belly button
• In front of the S2 vertebrae?

Question 8

What is a line of gravity?

Answer 8

• It’s an imaginary vertical line passing through the COG toward the center of the earth
• Demonstrates how exactly the force of gravity is pulling on an object

Question 9

What is the base of support?

Answer 9

• The area in contact with the ground AND the area between these contact points
• The contact points don’t need to be body parts (Ex: walkers, crutches)

Question 10

What are the four main factors that influence stability?

Answer 10

• Height of the center of gravity
• The base of support
• The location of the line of gravity relative to the base of support
• The weight of the body

Question 11

How does the height of the center of gravity affect stability?

Answer 11

• The higher the height, the more unstable the person is (and vise versa)
• Ex: stilts would be less stable then just standing on the ground

Question 12

How does the base of support affect stability?

Answer 12

• The size of the base of support affects stability
• As the size decreases, the stability decreases (and vise versa)
• Direction of depth of the base of support affects stability
• The greater surface area in the direction of the force applied, the greater the stability (and vise versa)
  ^ Think of the tightrope pushing we did in class

Question 13

How does the location of the line of gravity relative to the base of support affect stability?

Answer 13

• If the center of gravity is no longer over the base of support, the person will fall
• Think about when we tried to grab the pencil with our heals on the wall

Question 14

How does the weight of the body affect stability?

Answer 14

More mass = more stable (and vise versa)

Question 15

In general, who is more stable, men or women? Why?

Answer 15

• Women
• They have a lower center of gravity as they carry more weight in their hips and lower extremities than men do

Question 16

How does friction affect stability?

Answer 16

More friction = more stability (and vise versa)

Question 17

How does muscular effort affect stability?

Answer 17

When someone is in an unstable position, they require more muscular effort to remain there

Question 18

How does mobility affect stability?

Answer 18

• The more mobile someone is, the less stable they are (and vise versa)
• Fast movements = less stable (and vise versa)

Question 19

What are the three sensory components that affect stability?

Answer 19

• Vision
• Vestibular (inner ear)
• Proprioception / somatosensory