Movement Analysis pt 2

Question 1

Force of gravity, moment of force, center of mass, and newtons laws are all a component of kinematics or kinetics?

Answer 1

kinetics (effect of forces on the body vs kinematics- motion of a segment w out forces or torques)

Question 2

What is Newtons 1st law

Answer 2

A body remains in motion or at rest until an external force or torque is acted upon it

Question 3

According to Newtons 1st law, what is required to start, stop, accelerate, decelerate, or alter direction of movement

Answer 3

force

Question 4

Explain moment of inertia.
Does it have to do with linear or angular translation?

Answer 4

quantity that indicates resistance to a change in angular motion

angular

Question 5

what does moment of inertia depend on

Answer 5

mass of body

distance of CoM and axis

Question 6

Explain inertia

Answer 6

resistance to change state
- bus suddenly stop and upper body gets thrown foward
- when bus stop bod keeps moving forward bc of inertia

Question 7

explain how inertia is proportional to mass

Answer 7

more mass-> more resist to change of motion
- pencil easy to start or stop moving
- fridge- heavier, harder to start or stop

on bus- heavier person would lurch forward more

Question 8

Define Center of Mass

Answer 8

Point where all mass of an object is evenly distributed

Question 9

What parts of your body can be assigned a CoM?

Answer 9

segments and combo of segments

Question 10

How can CoM be changed

Answer 10

depending on where mass is positioned

Question 11

Where is CoM in standing? Sitting?

Answer 11

Standing- anterior to S2
Sitting- Inferior to axilla

Question 12

What is the most constant and influential force in regard to CoM?

Answer 12

gravity- it acts on an object at the CoM

Question 13

Gravitational force vector= _______
Gravity pulls vertically_____ towards earth

Answer 13

Line of Gravity
downward

Question 14

What can you manipulate to change inertia? Give example

Answer 14

Distance of CoM to the axis
changing position of body- Leaning trunk forward during sit-to-stand brings CoM closer to hip axis → reduces inertia → makes movement easier

Question 15

Would the moment of inertia be greater for the straight leg or bent leg?

Answer 15

straight leg bc CoM is further from Axis of rotation

Question 16

What is Newtons 2nd law of acceloration?

Answer 16

F=MA:

How much your body is able to move depends on how much FORCE is applied, how much MASS the object has, and how QUICKLY motion is changed

Question 17

what 2 things together make torque

Answer 17

moment of inertia and angular acceleration

Question 18

What does a decreased moment of inertia do to angular velocity and torque requirments?

Answer 18

increase angular velocity

decrease torque requirments

Question 19

Explain why i bend arms when running in terms of inertia

Answer 19

moment of inertia is greater

Question 20

Which sit up position is easiest and why? Which laws do these incorporate

Answer 20

Bottom, smaller distance between CoM to the axis

1st and 2nd- why?

Question 21

What is newtons 3rd law?

Answer 21

Every action has an equal opposite reaction
- every force that one body exerts on another is counteracted by a reciprocal force simultaneously

Question 22

Compared to walking is the GRF exerted on the body larger or smaller when running

Answer 22

Larger, more force down on the ground somewhere comes up