Unformatted text preview: Torques, Moments of Force, & Angular Impulse Angular
Course Reader: p. 61 85 Causes of Motion Causes
Linear Translation F = m*a What happens when you move the point of force application? Causes of Motion Causes
MOMENT (N*m): cause of angular rotation MOMENT Force (N) applied a perpendicular distance (m) from the axis of rotation. M = F * d⊥ M
⊥ F Axis of Rotation Axis Perpendicular distance from the point of force application to the axis of rotation application d d⊥ ⊥ F Known: Known: F = 100 N d = 0.25 m d
M M=F*d MOMENT (Nm) is a vector; magnitude & direction magnitude
F CCW +
d
M
⊥ M CW M  “Righthand Rule” Righthand Rule Righthand
CCW +
M Thumb Thumb Orientation: Orientation: Positive Torques Up Out of the page Negative Torques Down Into the page Moments at the Joint Level Moments
Static Equilibrium ΣM = 0
CCW Known: Ws = 71 N Ws
A&H +
M m A&H S Axis of Rotation: Center of Mass Axis
Center of Mass (CM, CoG, TBCM) • The balance point of an object Object of uniform density; CM is located at the Geometric Center Axis of Rotation: Center of Mass Axis
Center of Mass (CM, CoG, TBCM) • The balance point of an object Object of nonuniform density; CM is dependent upon mass distribution & segment orientation / shape. Axis of Rotation: TBCM Axis
CM location is dependent upon mass distribution CM & segment orientation segment Moments are taken about the total body center of mass.
CM CM CM CM Moments about the total body center of mass (TBCM) of
Long jump takeoff
Known: Fv = 7500N Fh = 5000N
⊥ v h CM ⊥ ⊥ Fh Fv Moments about the TBCM Moments
Long jump takeoff
Known: Fv = 7500N
⊥ v CM ⊥ Fv Moments about the TBCM Moments
Long jump takeoff
Known: Fh = 5000 N
⊥ h CM ⊥ Fh Moments about the TBCM Moments
Long jump takeoff Net Rotational Effect
v
Net CM ⊥ ⊥ Fh Fv Angular Impulse Moment applied over a period of time Σ Mcm ∆ t = Icm ∆ω h
h Angular Impulse taken about an object’s CM = the object’s change in angular momentum
Angular Momentum the quantity of angular motion Σ M = I α Σ M = I ∆ω / ∆ t Moments about the TBCM Moments
sprint start Known: Fv = 1000 N Fh = 700 N
⊥ Mv
CM ⊥ Mh Fh
⊥ Fv Moments about the TBCM
sprint start
Known: Fv = 1000 N Mv Mv
CM ⊥ ⊥ Fv Moments about the TBCM
sprint start
Known: Fh = 700 N
⊥ CM ⊥ Mh Mh Fh Moments about the TBCM
sprint start Net Rotational Effect
v
Net CM ⊥ Fh
⊥ Fv Angular Impulse Moment applied over a period of time Σ Mcm ∆ t = Icm ∆ω h
h Creating Rotation
Reposition your CM relative to Reaction Force
Horizontal RF Vertical RF 2500 2000 Force (N) 1500 1000 500
VRF 0.2 BACK Somersault
⊥ 0 0.1  500 0 FH FV
time prior to takeoff 0.5 0.4 0.3 d⊥ Time Prior to Takeoff (s) FV takeoff Rotational Demands of a Diver
Front Reverse Back Inward FH Force Force primarily responsible for Net rotation: rotation: F F FH F FH Takehome Messages Takehome
M (Nm) = F (N) * d⊥ (m) Righthand Rule: used to determine moment direction Static Equilibrium: Σ M = 0 Center of Mass (CM, TBCM) – balance point of an object – Position dependent upon mass distribution & segment orientation • At the totalbody level, moment created by the GRF’s taken about TBCM. Where moment arm length = perpendicular distance from CP location to TBCM location (dx & dy) • Moments are generated to satisfy the mechanical demands of a given task (total body, joint level, etc) • • • • ...
View
Full Document
 '10
 McNittGray
 Angular Momentum, Moment Of Inertia, Rotation, cm cm cm, FH Force Force

Click to edit the document details