L19-20;C13

Question 1

When is static equilibrium achieved?

Answer 1

This is achieved if the resultant external forces and torques acting upon an object is equal to zero

Question 2

Static equilibrium according to Newton’s first law means:

Answer 2

The object is not accelerating

Question 3

How are the resultant external forces and torques calculated?

Answer 3

By using vector compositions

Question 4

What is a dynamic equilibrium?

Answer 4

Concept indicating a balance between applied forces and internal forces for a body in motion

Question 5

We can treat a system as a _______ point in space and mathematically it has the same effect if you _________________________

Answer 5

Single, track every point in the body

Question 6

_____ can be considered concentrated at the CoG when analyzing linear kinetics of motion

Answer 6

Mass

Question 7

What happens when mass distribution within an object is not constant?

Answer 7

The CoG shifts in a direction of greater mass

Question 8

What are the two methods that can be used to calculate the CoG in the human body?

Answer 8

1. Reaction board methods

2. Segmental methods

Question 9

Where are there heavier segments? What happens to the CoM?

Answer 9

There are heavier segments in the trunk area, the CoM is mainly near the trunk for this reason.

Question 10

What does the term stability mean?

Answer 10

This is used to describe the ability of a system to withstand disturbance

Question 11

_____ ______ stability is ______ stability and refers to the entire combination of segments stability

Answer 11

Whole body, postural

Question 12

Load bearing capacity of musculoskeletal structures is classified as what kind of stability?

Answer 12

Joint stability

Question 13

Explain the following:

Force torque perspective of stability

Mechanical energy perspective of stability

Answer 13

Force torque perspective: considers the amount of torque and force required to disrupt equilibrium

Mechanical energy perspective: considers the amount of mechanical work required to disrupt equilibrium

Question 14

Explain the following force torque perspective terms and give example.

Stable equilibrium

Unstable equalibrium

Neutral equilibrium

Answer 14

Stable equilibrium- when large forces and torques are required to disrupt equilibrium position. Think of triangle on its base and being pushed over.

Unstable equalibrium- if very little force or torque is required to disrupt the current state. Think of triangle on its top balancing and being pushed

Neutral equilibrium- when an object has no tendency to move in one direction or other. Think of ball on flat leveled area. Doesn’t move or want to.

Question 15

The higher up an object is, the more ______ energy it’ll have due to the equation Mgh

Answer 15

Potential

Question 16

With respect to mechanical energy perspectives explain the following:

Stable equlibrium

Unstable equilibrium

Neural equilibrium

Answer 16

Stable equlibrium- when an object is in state of minimum potential energy

Unstable equilibrium- when an object has a state of maximal potential energy

Neural equilibrium- when a state of constant potential energy is applied

Question 17

What are the five factors that influence stability of equilibrium?

Answer 17

1. Mass of object
2. Friction
3. Size of BoS
4. Height of objects CoM/Cg [more PE->Higher CG, decreases stability]
5. Relationship of Cg and Bos

Question 18

What force is the only force acting on bodies CG since its constantly changing?

Answer 18

Gravity

Question 19

What is the inverted pendulum representing?

Answer 19

Postural sway

Question 20

Angular velocity and angular acceleration of body are affected by changes in _______ between body weight and vertical ground reaction force

Answer 20

Distance

Question 21

For larger perturbations, we use a ______ ______ which is used to increase BoS

Answer 21

Compensatory step

Question 22

When is it easier to initiate a rotation?

Answer 22

When force is applied perpendicularly and as far away from AoR

Question 23

1st class lever has:
2nd class lever has:
3rd class lever has

Answer 23

1st class lever has: force weight at equal ends and fulcrum in middle (force and weight producing same direction torques)

2nd class lever has: fulcrum at end, force at other end and weight near fulcrum (weight producing negative torque, force producing positive)

3rd class lever has: fulcrum at end, force near fulcrum, weight at end (weight producing negative torque, force producing positive)

Question 24

Three conditions must be met in order to be in static equilibrium:

Answer 24

1. Sum of all vertical forces acting on body=0
2. Sum of all horizontal forces acting on body= 0
3. Sum of all torques=0