Moments_AngularImpulse

Moments_AngularImpulse - Torques, Moments of Force,...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

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 - “Right-hand Rule” Right-hand Rule Right-hand 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 non-uniform 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 take-off Known: Fv = 7500N Fh = 5000N ⊥ v h CM ⊥ ⊥ Fh Fv Moments about the TBCM Moments Long jump take-off Known: Fv = 7500N ⊥ v CM ⊥ Fv Moments about the TBCM Moments Long jump take-off Known: Fh = 5000 N ⊥ h CM ⊥ Fh Moments about the TBCM Moments Long jump take-off 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 take-off -0.5 -0.4 -0.3 d⊥ Time Prior to Take-off (s) FV take-off Rotational Demands of a Diver Front Reverse Back Inward FH Force Force primarily responsible for Net rotation: rotation: F F FH F FH Take-home Messages Take-home M (Nm) = F (N) * d⊥ (m) Right-hand 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 total-body 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

Ask a homework question - tutors are online