Lec12_Sum_f - Summary Lecture 12 A quantity called...

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1 Lecture 12 Collisions in One and Two Dimensions Center of Mass Physics 111, Summer 2011, July 5, Lecture 12 Summary Linear momentum is the product of the r r A quantity called “linear momentum” incorporates the ideas of mass and velocity similar to kinetic energy but the linear momentum is a vector quantity. mass and the velocity of any moving object: Second Newton’s Law in terms of linear momentum: v m p t p t v m t v m a m F Δ Δ = Δ Δ = Δ Δ = = r r r r r ) ( If the total external force acting on the system is zero, the total momentum of the system is conserved: const p p p B A total = + = 2 Force acting on an object during any collision: Impulse (change in linear momentum = force x time): t F p Δ = Δ r r t p F Δ Δ = r r Physics 111, Summer 2011, July 5, Lecture 12 Collisions Collision : any strong interaction during relatively short time between moving relatively each other objects. There are two major parameters, which can be discussed for any collision: Types of collisions: 1. Linear momentum. 2. Kinetic energy. Elastic collision : The total kinetic energy of the system is the same after the collision as before. 3 Inelastic collision : The total kinetic energy of the system after the collision is less than before. The linear momentum of the system always is conserved (is the same after the collision as before). Physics 111, Summer 2011, July 5, Lecture 12 Elastic Collision Linear momentum and kinetic energy of the system are conserved : after the collision they are the same as those before. After the collision, two objects move separately . fin B B fin A A init B B init A A fin init v m v m v m v m or p p ) ( ) ( ) ( ) ( + = + = inetic energy before and after collision: Linear momentum of two objects before and after collision: 4 fin B B fin A A init B B init A A fin init v m v m v m v m or KE KE + = + = 2 2 2 2 2 2 2 2 Kinetic energy before and after collision: Physics 111, Summer 2011, July 5, Lecture 12
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2 Elastic Collision (#1) A 1000 kg car moves at 3 m/s and hits a stationary 2000 kg truck. After
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Lec12_Sum_f - Summary Lecture 12 A quantity called...

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