KIN 360--Exam 1 Terms

kinesiology

the analysis of human motion

origin

a location from which all measurements will be taken

synonym of perpendicular lines

orthogonal lines

biomechanics

the interdisciplinary science that applies the principles of mechanics to the study of biological systems

kinematics

the branch of mechanics that deals with the %%**description of motion**%%

kinetics

the branch of mechanics that studies the __**actions of forces**__ in producing or changing the motion of masses

sagittal

aka. anteroposterior; a vertical plane passing through the body from front to back, dividing it into equal left and right halves

frontal

aka. lateral or coronal; a vertical plane passing through the body from side to side, dividing it into anterior and posterior halves

transverse

aka. horizontal; a horizontal plane passing through the body from side to side, dividing it into upper and lower halves

center of mass (informal definition)

the intersection of the three cardinal planes

fundamental standing position

anatomical position but arms are held to the side

contralateral

pertaining to the opposite side

inversion

lifting the medial border of the foot

eversion

lifting the lateral border of the foot

abscissa

distance along the x-axis away from the y-axis

ordinate

distance along the y-axis away from the x-axis

scalar

variables that possess only a magnitude

vector

variables that contain both a magnitude and a direction

point of application

the exact location at which a force is acting on a body

line of action

a straight line extending infinitely in both directions from the line segment representing the vector

law of transmissibility

vectors may be shifted along their line of action for the purposes of mathematical manipulation

vector composition

replacing a vector system by a single vector, aka the addition of two or more vectors to form a single vector (the resultant) with the same physical interpretation

vector resolution

the breakdown of a vector into two component vectors

displacement

the difference in position between an object’s starting point and the object’s ending point; amount or size in change of position

center of rotation

usually a joint, the spot that angular motion works around

linear displacement

shortest distance between two points

angular displacement

shortest angle between two points

mass

quantitative measure of inertia

inertia

an object’s inherent resistance to change its state of motion

Newton’s first law

every body persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it

momentum

the quantity of motion an object possesses (kg \* m/s)

Newton’s second law

the rate of change of momentum of a body is proportional to the applied force and takes place in the direction in which the force acts

a force is equal to the rate of change of…

momentum

center of mass

the balance point of the body in all three planes of motion

center of gravity

where the cardinal transverse plane intersects the vertical axis

what does a force platform measure?

forces along all three axes

impulse

a measure of what is required to change the motion of an object (a vector quantity)

Newton’s third law

to every action there is always opposed an equal reaction; or, the mutual action of two bodies upon each other are always equal, and directed to contrary parts

gravitational attraction

all bodies attract one another with a force proportional to the product of their masses and inversely proportional to the square of the distance between them

normal force

the force exerted by two objects orthogonal (perpendicular) to the contact surfaces between them

limiting friction (Fs)

the limit of the force that can be applied to an object before movement begins to take place

what causes limiting friction?

microscopic irregularities in the contact surfaces of the two objects

what does limiting force measure?

the amount of force that two objects can produce to keep themselves from sliding across one another

when a force applied to an object results in a displacement, ____ has been performed

work

positive work

work performed in the same direction as the applied force

negative work

work performed in the opposite direction of the applied force

energy

the capacity to do work

how can we express work in terms of energy?

it is the change in the sum of all forms of energy used by the body

potential energy

energy an object possesses due to its position

mass (kg) \* height (m) \* g (m/s2) or Nm

what is a joule?

a measure of energy

kinetic energy

energy an object has due to its motion

1/2mv2

mechanical energy

the sum of the potential and kinetic energies

power

the measure of the rate of work performed

coefficient of static friction

ratio of an object’s limiting friction to the normal force

moment arm

the perpendicular distance (d)

moment (or torque)

the turning effect of a force

what are the two ways of calculating a moment?

1. the perpendicular component of a force \* the distance from its point of application to the center of rotation
2. F \* perpendicular distance from the point of application of that force to the center or rotation

equilibrium

when the sum of all forces and moments action on a body are zero

first class lever system

1. fulcrum is in the middle
2. changes direction of force
3. get out what you put in (equal)

second class lever system

1. resistance force applied between the fulcrum and the effort
2. eccentric contraction
3. weight is the effort
4. get more than what you put in

third class lever system

1. gives you range of motion
2. effort force applied between the fulcrum and the resistance
3. concentric contraction
4. get less than what you put in

mechanical advantage

the ratio of the magnitude of resistance force overcome by a lever to the magnitude of the effort force applied

moment of inertia

the measure of a body’s inherent resistance to alter its state of angular motion (angular velocity)

angular momentum

the quantity of angular motion an object possesses

law of conservation of angular momentum

the total angular momentum of a rotating body will remain constant unless acted upon by an external moment

principle of levers

a lever of any class will balance when the product of the effort and the effort arm equals the product of the resistance and resistance arm

|E| \* EA = |R| \* RA

rearranged… (|E| \* EA) - (|R| \* RA) = 0

coefficient of static friction

μs = Fs / N

\

acceleration

a = vf - vi / t

kinetic energy

Ek = 1/2mv2

half of the object’s mass multiplied by the velocity of the object squared

unit = joules (J) or Nm (newton-meters)

potential energy

Ep = mgh

mass multiplied by the gravitational constant multiplied by height

Unit = joules (J)

mechanical energy

Em = Ek + Ep

sum of the kinetic and potential energies

unit = joules (J) or Nm

work (scalar)

W = F \* d

power (scalar)

P = F \* d/t or W/t

unit = watts (w)

work (angular)

W = M \* θ

rotational moment multiplied by the angular displacement

power (angular)

P = M \* ω

rotational moment multiplied by the angular velocity

momentum

M = mv

product of mass and velocity

unit = kg \* m

force (momentum)

F = (mvf - mvi) / t

rate of change of momentum

units = newtons (N)

impulse (equation)

Ft = mvf - mvi

change in momentum

unit = Nm, newton-meters

gravitational force

F = G (m1 \* m2 / r2)

Unit = Newtons (N)

moment

M = F x d (perpendicular) or F (perpendicular) x d

Unit = Nm (Newton-meters)

mechanical advantage

MA = R/E

resistance force divided by effort force

moment of inertia

I = mr2

the product of an object’s mass and the radius squared

unit = kg\*m2

angular momentum

H = Iω

the product of a moment of inertia and angular velocity

unit = kg\*m2/s

moment (angular)

M = Iα

product of the moment of inertia and angular acceleration

unit = Nm (newton-meter)

average angular velocity

**ω**avg = Δ