Linear Kinetics

Question 1

What do we need to know to adequately describe a force?

Answer 1

• magnitude
• direction
• point of application

Question 2

mass (kg)

Answer 2

amount of matter constituting the body

Question 3

weight (N)

Answer 3

mass * gravity

F = M*a

Question 4

center of mass

Answer 4

point about which the matter of a body is evenly distributed

Question 5

object supported by _____ will balance and rotate freely

Answer 5

COM

Question 6

T or F? COM may be in a location with no mass

Answer 6

true

Question 7

COM - the point about which the sum of torques =

Answer 7

zero

Question 8

law of inertia

Answer 8

every body at rest, or moving at a constant velocity in a straight line will continue in that state unless compelled to change by an unbalanced external force exerted upon it

Question 9

movement is ____ in the absence of a net external force

Answer 9

constant

Question 10

momentum =

Answer 10

m*V

Question 11

law of acceleration

Answer 11

the acceleration of a body is proportional to the net force causing it and takes place in the direction in which the net force acts
SumF = m*a

Question 12

law of action/reaction

Answer 12

for every force that is exerted by one body on another, there is an equal and opposite force exerted by the second body on the first
- for every action there is an equal and opposite reaction

Question 13

joint reaction force

Answer 13

• equal and opposite forces that exist between adjacent bones at a joint caused by the weight and inertial forces of the two segments
• the net force acting across the joint

Question 14

what are the internal forces resolved into components?

Answer 14

• rotary (shear)
• stabilizing (compressive)
• dislocating (tension)

Question 15

what is the primary external force we’re concerned with?

Answer 15

gravity! it’s inherent in pt. evaluation and exercise prescription
- effect of gravity on joint torque will vary throughout the range of motion

Question 16

acceleration of an object occurs only when there is an _____-

Answer 16

imbalance of force

Question 17

what are two types of forces acting on a system?

Answer 17

• linear motion
• rotation and or translation motion

Question 18

what are two types of rotation and or translation motions?

Answer 18

• eccentric
• force couple

Question 19

What are two examples of force couples?

Answer 19

• humeral rotation without translation (most muscles do this)
• scapular rotation without translation (raise arm above head)

Question 20

T or F: muscles produce force of 5-15x greater than body weight to accelerate COM against gravity

Answer 20

True
joint forces in the body are much greater than vGRF (gravity)

Question 21

Impulse =

Answer 21

force * time
(often calculated as the integral (area) under the force-time curve

Question 22

momentum =

Answer 22

mass * velocity

Question 23

F = ma or….

Answer 23

F= m ((change v)/(t))

Ft = m(change v)

Ft = momentum final - momentum initial

Question 24

speeding up _________ impulse and _______ change in velocity of COM(for ant/post)

Answer 24

increases
increases

Question 25

slowing down _____ impulse and ______ change in velocity on COM (for ant/post)

Answer 25

decreases decreases

Question 26

___________ impulse with each stance phase accelerates CoM left and right

Answer 26

medial * known as serpentine pattern

Question 27

what is the only force that exists in presence of another force?

Answer 27

friction

Question 28

what is the force that resists sliding/slipping

Answer 28

friction

Question 29

T or F: there can be friction without movement

Answer 29

true

Question 30

Where does friction act?

Answer 30

at the point(s) of contact between contacting surfaces * always opposes motion between contacting surfaces

Question 31

friction magnitude is ________

Answer 31

variable

Question 32

static friction

Answer 32

resistance prior to sliding

Question 33

Fs is equal to

Answer 33

motive force

Question 34

kinetic friction

Answer 34

resistance one sliding occurs

Question 35

Fk is less than

Answer 35

motive force

Question 36

What are the factors affecting friction?

Answer 36

coefficient of friction normal force

Question 37

Friction force = (what is the formula)

Answer 37

u*N

Question 38

what does normal force do?

Answer 38

forces holding surfaces together is perpendicular to the supporting surface