Intro / Linear Kinematics Flashcards by Ella Bensz

what is biomechanics?

study of forces and their effects on living systems

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statics

mechanics of objects at rest or in uniform motion

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uniform motion

constant velocity, > 0m/s
acceleration is zero

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dynamics

mechanics of objects in accelerated motion

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kinematics

description of motion independent of the cause (what we observe)

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kinetics

forces that cause or change motion

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sagittal plane

vertical and AP axis

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frontal plane

vertical and ML axis

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transverse plane

AP axis and ML axis

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linear motion (translation)

along an axis

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angular motion (rotational)

around an axis
fixed axis
paths different lengths

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plane

a 2D surface defined by 3 points not on the same line (not colinear)

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motion

process in change in position over time

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rectilinear motion (rare)

motion along a straight line or path

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curvilinear motion (common)

motion along a curved line or path
no fixed axis
paths same length

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examples of angular motion

leg raises (internal axis)
swinging from a bar (external axis)

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qualitative kinematic analysis

visual observation of motion

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quantitative kinematic analysis

measurement

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most commonly used spatial reference system

Cartesian coordinate system

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global coordinate systems

1D, 2D, 3D

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local coordinate systems

relative angle & absolute angle

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relative angle (joint angle)

local CS relative to another local CS

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absolute angle (segment angle)

global GS relative to a local CS

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scalar

magnitude only

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vector

magnitude & direction

linear position

- location in space - avg or instananeous - ref point needed

example of linear position

shuttle run (no displacement)

distance (l)

- length of the path of motion - scalar

displacement (d or delta s)

- change in position in a specific direction - vector

displacement equation

Δs = s final - s initial

use of distance in gait analysis

left side stroke, shorter right step

what is a runner's displacement if they compete: a) one lap b) ten laps c) 1/2 lap

a) 0 m b) 0 m c) 200 m

calculating linear displacement with two coordinates

1) Δy = yf - yi, Δx = xf - xi 2) d = √Δx^2 + Δy^2

calculating direction (angle of resultant)

SOH CAH TOA

speed

- how fast a person or object is moving - scalar

speed equation

speed = distance / time

velocity

- how fast a person or object is moving in a specific direction - vector

velocity equation

velocity = displacement / change in time (Δposition / Δtime)

What is the resultant velocity if it tok a hiker 13 hrs and 45 min to hike from Yosemite National Park to Lake Tahoe? Map: 77 miles 60 degrees N of W = resultant displacement

1) convert miles to m and time to sec 2) v = Δposition / Δ time v = 123919 m / 49500 sec v = 2.5 m/s, 60 degrees N of W 3) direction: break into x and y components y-component = 2.5sin60 = 2.17 m/s N x-component = 2.5cos60 = -1.25 m/s W

T/F: a change in the body's velocity may represent a change in its speed, movement direction, or both

True

example of linear speed

gait speed

stride length x stride frequency *increasing one or the other increases gait speed*

A runner completes 6 1/2 laps around a 400 m track that has a diameter of 160 m. It takes the runner 12 min (720 s) to complete the run. Calculate the following: a) distance covered b) displacement at the end of 12 min c) average speed d) average velocity

a) 2600 m b) -160 m or 160 m south c) 3.61 m/s d) -0.22 m/s

most economical runner

lowest submaximal oxygen consumption (VO2)

most economical trunk angle

greater trunk lean (5.9)

most economical max. knee flexion in support

greater knee flexion (43.1)

most economical wrist excursion

- medium wrist excursion (80.7) - "goldilocks zone"

most economical vertical oscillation

lower levels of vertical oscillation (9.1)

Brian is trying to swim in the ocean from west to east at a velocity of 1.5 m/s. However, the water current is pushing him at an angle of 20 degrees west of south at a velocity of 0.5 m/s. What is Brian's resultant velocity?

1) break into x and y components 2) SOH CAH TOA 3) sum x components and y components separately 4) plug into resultant velocity equation Vr = 1/41 m/s θ = 70.53 degrees east of south

linear acceleration

the change in motion of an object

acceleration equation

acceleration = change in velocity / change in time (Δv / Δt)

EXAM: acceleration may be positive, negative, or zero, based on:

- direction of motion - change in velocity (slowing down, speeding up)

case 1: speeding up in the positive direction

+ velocity speeding up + acceleration (+)(+) = (+)

case 2: slowing down in the positive direction

+ velocity slowing down - acceleration (+)(-) = (-)

case 3: speeding up in the negative direction

- velocity speeding up - acceleration (-)(+) = (-)

case 4: slowing down in the negative direction

- velocity slowing down + acceleration (-)(-) = (+)

If a runner is slowing down in the positive direction: what is acceleration?

negative (+)(-) = (?)

A runner's final velocity is positive: Running in the positive direction. Acceleration is negative. Is the runner speeding up or slowing down?

slowing down (+)(?) = (-)

+ velocity, + acceleration

speed is increasing (speeding up)

- velocity, - acceleration

speed is decreasing (slowing down)

Andrea is running at a speed of 3.0 m/s in the negative direction at time 4 s. Her acceleration between time 4 s and 6 s was -2.5 m/s^2. Was she slowing down or speeding up?

speeding up (-)(?) = (-) or a = Δv / Δt solve for vf

to be able to identify sign (direction of acceleration, need to know:

- direction of motion (sign of velocity) - if v is increasing or decreasing (speeding up/slowing down)

to be able to identify if person/object is speeding up/slowing down, need to know:

- direction of motion (sign of velocity) - sign of acceleration

Intro / Linear Kinematics Flashcards

(64 cards)