King Fahd University of Petroleum & Minerals Mechanical Engineering Dynamics ME 201 BY Dr. Meyassar N. Al-Haddad Lecture # 18

Objective Newton First Law To study the conservation of linear momentum for particles

Principle of Linear Impulse and Momentum

Principle of Linear Impulse and Momentum for a system of Particles

Conservation of Linear Momentum for a system of Particles 0 Conservation of linear momentum equation

Applied when particles collide or interact Identify the forces and determine in what direction linear momentum is conserved Internal impulse will be cancelled “ Non impulsive force ” : small forces takes place in a short period which can be ignored. i.e. weigh of a ball “ impulsive force ” : very large force acting for a very short period of time and produce a significant change in momentum. i.e. explosion, accident

Impulse & Average Force Impulse

Free Body Diagram Considered the two objects as single system By inspection, establish the direction of the momentum is conserved Cancel the internal coupled force Assume the two object move with v 2 in positive direction if coupled Apply the conservation of linear momentum To assess the average force, isolate one object and apply the coupling force as external force. Then apply Apply the principle of impulse and momentum

Example 15-4 m A =15 Mg m B =12 Mg Couple together V 2 =? After coupling F avg = ? In 0.8 s

Example 15-5 W C =1200-Ib W p = 8-Ib v p =1500ft/s t = 0.03 s. v c2 = ? F avg = ? F avg

Impulse Impulse = Example 15-7 m p = 800 kg m H = 300 kg From rest Impulse = ? Couple together