Angular Kinetics 1

Question 1

What is torque

Answer 1

the tendency for an object to rotate about an axis caused by a force - a rotary force - the result of a force applied a certain perpendicular distance from an axis of rotation

Question 2

What are other terms for torque

Answer 2

moment of force

moment

Question 3

Can a force exist if the object isnt moving

Answer 3

yes

Question 4

What is torque dependent on

Answer 4

the size of the force and where the force is applied

Question 5

What is torque influenced by

Answer 5

• The line of action of the force (direction)
• Its point of application
  its magnitude

Question 6

What is the moment arm

Answer 6

the distance from an axis that a force is being applied

Question 7

The axis of rotation can be ___ or ____

Answer 7

fixed or free

Question 8

A fixed axis is a ____

A free axis is a ___

Answer 8

hinge

CofG

Question 9

The ____ can indicate the line of action of the muscles

Answer 9

tendons

Question 10

Is torque vector or scalar

Answer 10

vector

Question 11

The same force will create a different torque depending on…

Answer 11

the position of the arm

Question 12

In general we can determine the magnitude and direction of the moment about the joint by…

Answer 12

considering the external force line of action in relation to the joints we are interested in

Question 13

A negative moment causing ….

Answer 13

a negative rotation

Question 14

does muscle action and moments always coincide ?

Answer 14

no

but sometimes

Question 15

What is the purpose of lateral trunk bending

Answer 15

to reduce the forces in the abductor muscles and hip joint during single leg stance

Question 16

In normal early stance the line of action of the GRF vector passes ____ of the hip and generates _____. The Hip extensors opposes this with a…

Answer 16

in front
a hip flexor moment
hip extensor moment

Question 17

When does posterior trunk bending occur

Answer 17

If the gluteus maximus is weak or paralyzed

Question 18

With posterior trunk bending the line of action of the GRF passes ___ the axis of the hip and creates a _____ moment

Answer 18

behind

hip extensor moment

Question 19

What is the centre of mass

Answer 19

The point on a body where all of the mass of the object can be concentrated
The average location of all the mass in a body

Question 20

What is the centre of gravity

Answer 20

The point in a body system around which its mass or weight is evenly distributed or balanced and through which the force of gravity acts

Question 21

In traditional anatomical position, the heigh of a human centre of gravity is…

Answer 21

55-57% of your standing height

Question 22

How do you calculate the centre of gravity ?

Answer 22

the sum of all the masses times the radius, divided by the sum of all the masses

Question 23

The centre of gravity is a…

Answer 23

point of balance

Question 24

The force of gravity pulls down on all mass particles in the body, each element creates a _____ about the other elements

Answer 24

torque

Question 25

The centre of gravity is the position where...

Answer 25

the torques created by all the elements are balanced

Question 26

The total weight acts through the....

Answer 26

centre of gravity

Question 27

What are three ways to determine the CoG of segments in humans?

Answer 27

1. Reaction board change method 2. Cadaver limbs 3. Scanning techniques (photogrammetry, Dexa, MRI)

Question 28

What are two downside to the reaction board method for determining centre of gravity

Answer 28

takes very long and is not very specific to different body parts

Question 29

How does the reaction board method work for determining centre of gravity

Answer 29

sum all torques around pivot point, wince we can find the weight of the individual and have the scale reading

Question 30

How can we determine the mass of CoG of different segments?

Answer 30

Reaction board + force plate - mass and CofG location. Calculate torque in different postures

Question 31

How do photogrammetry, dual-energy X-ray Absorbtiometry and magnetic resonance imaging images can be...

Answer 31

segmented and then known values for fat, muscle and bones are used to determine body segment parameters

Question 32

If you lift your left arm to your side you CoG...

Answer 32

.shifts to the left and moves up slightly

Question 33

Why does your CoG shift

Answer 33

because you have changed the distribution of the weight in your body. You stil lhave the same amount of weight on both sides but the moment arm of the weight of your arm is greater than it was so the torque is greater as well. To balance out the extra torque the centre of gravity shifts to the left

Question 34

For each limb movement the CoG of the entirebody shifts in the direction of....

Answer 34

that movement

Question 35

What does how much the CoG moves depend on?

Answer 35

the weight of the limb that moved and the distance it moved (torque caused by the limb)

Question 36

Are centre of gravity and centre of pressure the same??

Answer 36

NO

Question 37

What is the centre of pressure

Answer 37

This is the point location of the vertical ground reaction force vector. It represents a weighted average of all the pressures over the surface of the area in contact with the ground

Question 38

If one foot is on the ground, the net CoP lies...

Answer 38

within that foot

Question 39

at different points in the walking cycle the GRF vector acts... and creates....

Answer 39

at the centre of pressure under one foot and creates a torque about the CoG

Question 40

During quiet standing the movement of the COP moves...

Answer 40

in such a way to minimize the movement of the COG.

Question 41

The CoP oscillates around the position of the CoG creating...

Answer 41

opposing righting moments

Question 42

The ___ will move back and forth trying to keep the ___ within the base of support

Answer 42

COP | COG

Question 43

When you apply force to an object anywhere but its centre of gravity the object will...

Answer 43

translate and rotate about its centre

Question 44

A force not through the centre tends to cause... why?

Answer 44

a change in both the angular and linear motion of an object | Because the object will have tendency to rotate about its center of gravity