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Ch 15 Notes – Part 2. 15.4 Impact. Central Impact Oblique Impact Line of Impact Plane of Impact. Ch 15 Notes – Part 2. 15.4 Impact. Ch 15 Notes – Part 2. 15.4 Impact. Coeff of Restitution e = (vB2 – vA2)/ (vA1 – vB1) Plastic impact, e = 0 Elastic impact, e = 1
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Ch 15 Notes – Part 2 15.4 Impact • Central Impact • Oblique Impact • Line of Impact • Plane of Impact
Ch 15 Notes – Part 2 15.4 Impact
Ch 15 Notes – Part 2 15.4 Impact • Coeff of Restitution • e = (vB2 – vA2)/ (vA1 – vB1) • Plastic impact, e = 0 • Elastic impact, e = 1 • Can never achieve this exactly
Ch 15 Notes – Part 2 15.5 Angular Momentum • The angular momentum of a particle about point O is defined as the “moment” of the linear momentum about O. • (Ho)z = (d)(mv), where d is the moment arm or perpendicular distance from O to the line of action of mv
Ch 15 Notes – Part 2 15.5 Angular Momentum • Ho = r x mv • Ho = | i j k | • | rxryrz | • | mvxmvymvz|
Ch 15 Notes – Part 2 15.6 Relationship Between Force and Angular Momentum • Mo = Hodot = r x mvdot • The resultant moment about O of all the forces acting on the particle is equal to the time rate of change in the particle’s angular momentum
Ch 15 Notes – Part 2 15.6 Relationship Between Force and Angular Momentum • F = mvdot • F = Ldot • The resultant force acting on the particle is equal to the time rate of change in the particle’s linear momentum
Ch 15 Notes – Part 2 15.6 Relationship Between Force and Angular Momentum for a System of Particles • Mo = Hodot • The sum of the moments about O of all the external forces acting on a system of particles is equal to the time rate of change in the system’s angular momentum about O
Ch 15 Notes – Part 2 15.6 Relationship Between Force and Angular Momentum • When the angular impulses acting on a particle or a system of particles during time t1 to t2 are zero, angular momentum is conserved. • (Ho)1 = (Ho)2