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Published byLisa Singleton Modified over 9 years ago
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Ch 9 Notes
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Momentum: inertia in motion ρ = m v ρ (rho) units of kgm/s VECTOR QUANTITY Inertia of an object depends on its mass AND velocity Impulse = Change in Momentum units of Ns Based on definitions of acceleration: a = F/m & a = Δ v/t so F/m = Δ v/t Cross multiply to get F t = m Δv
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Impulse = Change in Momentum units of N*s Impulse (I) = FΔt A measure of how quickly momentum changes. Or how quickly a force acts upon an object.
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Large Force, Little Time Little Force, Larger Time
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For closed systems, the sum of the momenta must be conserved between the objects in the system. Σρ initial = Σρ final Nonstick perfectly elastic m 1 v 1i + m 2 v 2i = m 1 v 1f + m 2 v 2f Sticky inelastic m 1 v 1i + m 2 v 2i = (m 1 +m 2 ) v f
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If momentum must be conserved, then… The impulse of an object and its momentum must be conserved, so… ρ = m v and I = FΔt Therefore: mΔv = FΔt for objects in the same system
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What is the momentum of a 250kg car that is traveling at 9 m/s?
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What is the impulse of a ball that collides with a wall in.03s with a force of 150N?
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What is the change in momentum of an object that has collides with a wall with an impulse of.15 N*s?
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Review LOCOE Quizzes Review Impulse and Momentum Momentum Lab Collisions
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Warm-Up Electrostatics Conservation of Momentum Lab Exploding Carts!! Change in Momentum: Collisions
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Elastic Collisions Two objects collide and bounce off of one another Ex: Tennis ball and racket Momentum is conserved m 1 v 1i + m 2 v 2i = m 1 v 1f + m 2 v 2f
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Inelastic Collisions Two objects collide and stick together Two masses become one mass moving at a slower velocity m 1 v 1i + m 2 v 2i = (m 1 +m 2 ) v f
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A 2kg bowling ball is rolled into a.5kg pin. The ball is moving with a velocity of 2.5m/s and collides elastically with the pin. After the collision the ball is moving at.25 m/s. How fast was the pin moving after the collision?
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Circuits Warm-Up Need calculators Momentum and Impulse Lab Complete Collision Problems and turn in on calcs Momentum/Impulse Quiz Monday
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Wear goggles No one else should be near the table when you chop You must chop THROUGH the board If you stop at the board you will hurt yourself Close your fingers when you chop If you don’t you could hurt them
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