Momentum
Momentum is inertia in motion
momentum = mass x velocity
p = mv
Impulse Changes Momentum
Impulse is the change in momentum
impulse = force x time interval
impulse = change in (mass x velocity)
force x time interval = change in (mass x velocity)
Ft = change in mv
Newton's 2nd Law
net F = ma
net F = m (vf - vo) / t
(net F)t = m (vf - vo)
(net F) t = mvf - mvo
(net F)t = pf - po
(net F)t = Δp
impulse = the change in momentum
Newton's 3rd Law
FAB = - FBA
FAB t = - FBA t
mBvfB - mBvoB = - (mAvfA- mAvoA)
mBvfB + mAvfA = mAvoA + mBvoB
Σpf = Σpo
The Law of Conservation of Momentum states the sum of the momenta before a collision equals the sum of the momenta after a collision
Bouncing
Lab: Bounce Momentum: Bouncing Balls Lab
In this activity, students examine how different balls react when colliding with different surfaces. Also, they will have plenty of opportunities to learn how to calculate momentum and understand the principle of conservation of momentum.
LEARNING TARGETS
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Understand that momentum depends on both mass and velocity.
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Recognize that different surfaces and materials promote different types of collisions.
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Collect data to solve equations.
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Learn that understanding material properties is an important aspect of engineering design
Conservation of Momentum
If no outside force is present no change in momentum is posible
Collisions
Elastic Collisions
follows the Law of Conservation of Momentum
"the total amount of momentum before a collision is equal to the total amount of momentum after a collision."
the total kinetic energy of the system (all the objects that collide) is conserved during an elastic collision.
Inelastic Collisions
follows the Law of Conservation of Momentum
"the total amount of momentum before a collision is equal to the total amount of momentum after a collision."
the total kinetic energy of the system (all the objects that collide) is NOT conserved during an elastic collision.
Momentum Vectors
Lab: PhET Collision Lab: Introduction in One Dimension
In this activity, students will use a virtual air hockey table to investigate simple collisions in 1D and more complex collisions in 2D. Experiment with the number of discs, masses, and initial conditions. Vary the elasticity and see how the total momentum and kinetic energy changes during collisions.
LEARNING TARGETS
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Draw "before-and-after" pictures of collisions.
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Construct momentum vector representations of "before-and-after" collisions.
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Apply the law of conservation of momentum to solve problems of collisions.
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Explain why energy is not conserved and varies in some collisions.
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Determine the change in mechanical energy in collisions of varying “elasticity”.
What does “elasticity” mean?