Lecture_10

Lecture_10 - conserved This will be true for a system of...

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Momentum, Impulse, and Collisions

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Momentum Some objects can be described as point particles Some objects need to be considered as a collection of particles. p=m { v ¿ p tot = p i = m i v i
Force and Momentum If there is no net force, there is no acceleration (no change is velocity) so momentum does not change (Newton's 1 st Law) If there is a non-zero net force, there will be acceleration (the velocity will change), so momentum will change (Newton's 2 nd Law) impulse= { F Δt=Δp ¿ Impulse Theorem Example: What is the direction of the impulse imparted by the racket to the ball?

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Time of Collision
Collisions Two objects that collide with each other exert forces on each other. These objects will be an action-reaction pair so the force exerted by the first object on the second object is equal in magnitude and opposite in direction to the force exerted by the second on the first. Rewritten in terms of momentum: That is, the total momentum of the system of two particles does not change – it is

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Unformatted text preview: conserved. This will be true for a system of any number of particles that are not acted on by an external force Δ ⃗ p 1 =−Δ ⃗ p 2 Δ ⃗ p 1 +Δ ⃗ p 2 =Δ ⃗ p tot = Momentum Carts Cylinder Momentum Explosion Collisions Elastic collision – Both kinetic energy and momentum are conserved (no heat losses). Inelastic collision – Some kinetic energy is lost to heat, sound, light, etc. (momentum is still conserved). Many examples are given in the chapter. Bowling Balls (elastic v. inelastic) Carts (elastic v inelastic) Newton's Cradle / Astroblaster Center of Mass Center of mass allows us to predict the motion of an extended body (made of many point particles). x cm = ∑ i m i x i ∑ i m i = ∑ i m i x i M tot y cm = ∑ i m i y i ∑ i m i = ∑ i m i y i M tot Locating Center of Mass (USA / cork and forks) Overhanging blocks Motion of Center of Mass Motion of the center of mass can only be caused by outside forces....
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Lecture_10 - conserved This will be true for a system of...

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