Linear Momentum

# Linear Momentum - Linear Momentum The linear momentum p of...

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Linear Momentum The linear momentum p of an object with mass m and velocity v is defined as From this definition it is clear that the unit of momentum is (kg m/s) or (N s). Since this momentum is related to the linear motion of the object, it is called linear momentum. In Chapter 11 we will be discussing angular momentum which is the momentum related to the angular motion of the object. Under certain circumstances the linear momentum of a system is conserved. The linear momentum of a particle is related to the net force acting on that object: The rate of change of linear momentum of a particle is equal to the net force acting on the object, and is pointed in the direction of the force. If the net force acting on an object is zero, its linear momentum is constant (conservation of linear momentum). The total linear momentum p of a system of particles is defined as the vector sum of the individual linear momenta This expression can be rewritten as where M is the total mass of the system. We conclude that " The linear momentum of a system of particles is equal to the product of the total mass M of the system and the velocity of the center of mass. " If we differentiate linear momentum of the center-of-mass with respect to time we obtain This expression shows that if the net external force acting on a system of particles is zero (F ext = 0 N), the linear momentum of the system is conserved. Example Problem 9-4 A stream of bullets with mass m is fired horizontally with speed v into a large wooden block with mass M that is initially at rest on a horizontal table. If the block is free to slide across the table (without friction), what speed will it acquire after it has absorbed n bullets ? Figure 9.7. Example Problem 9-4.

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## This document was uploaded on 11/25/2011.

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Linear Momentum - Linear Momentum The linear momentum p of...

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