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Chapter 8: Momentum Conservation. Impulse. Work. Distance, l. K = (1/2) m v 2 Work-Energy Theorem Energy Conservation. p = m v Impulse-Momentum Theorem Momentum Conservation. 1D Collision. M. m. M. m. Elastic Collision. Energy Conservation. Loss of energy as thermal and
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Chapter 8: Momentum Conservation Impulse Work Distance, l K = (1/2) m v2 Work-Energy Theorem Energy Conservation p = mv Impulse-Momentum Theorem Momentum Conservation Momentum Conservation
1D Collision M m M m Momentum Conservation
Elastic Collision Momentum Conservation
Energy Conservation Loss of energy as thermal and other forms of energy Momentum Conservation
Example 2 After collision Before collision (totally inelastic collision) m v1 + m v2 = m v1’ + m v2’ v1’ =v2’ Momentum Conservation
Impulsive Force [Example] an impulsive force on a baseball that is struck with a bat has: <F> ~ 5000 N & Dt ~ 0.01 s Very large magnitude Impulsive Force Very short time [Note] The “impulse’’ concept is most useful for impulsive forces. Momentum Conservation
Impulse-Momentum Theorem 1D |J | 2D Momentum Conservation
Momentum Conservation y x Momentum Conservation
Example 3 Express vand v’ in terms of m, M, g, and h. • (A) mv = (m+M) v’ • (B) K1+Ug1 = K2+Ug2 (A) Momentum Conservation 2 1 (B) Energy Conservation Momentum Conservation
Example 1 • What is the impulse given the • wall ? Note: m = 0.060 kg. • Dpx, and Dpyfor the ball • J(on the wall) = - J(on the ball) py,f vf = 28 m/s px,f (1) Coordinates (2) J(on the ball) Dpx = px,f - px,i = - 2 xpx,i Dpy = py,f - py,i = 0 where: px,i = m vi sin q = 1.2 N*s py,i px,i y vi = 28 m/s x Momentum Conservation
1D/2D “Explosion’’ 1 2 (or more) Momentum Conservation
Center of mass Center of Mass (c.m. or CM) The overall motion of a mechanical system can be described in terms of a special point called “center of mass” of the system: Momentum Conservation
CM Position (2D) m3 ycm = 0.50 m X m1 + m2 X m1 m2 + m3 xcm = 1.33 m Momentum Conservation
CM Position and Velocity 48.0 m t = -2 s x t = 0 s m v1 + m v2=(m + m) v’ (totally inelastic collision) Momentum Conservation
2D Collision Momentum Conservation