Objectives Students should be able to: 1. Define linear momentum and calculate it. 2. Distinguish...
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![Page 1: Objectives Students should be able to: 1. Define linear momentum and calculate it. 2. Distinguish between the unit of force and momentum. 3. design an.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649d705503460f94a52105/html5/thumbnails/1.jpg)
ObjectivesStudents should be able to:
1. Define linear momentum and calculate it.2. Distinguish between the unit of force and momentum.3. design an experiment in order to make conclusions about the total momentum in a system before and after a collision or explosion.
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Let’s start with everyday language
What do you say when a sports team is on a roll?
They may not have the lead but they may have ___________
MOMENTUM
A team that has momentum is hard to stop.
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Momentum Defined
p = m v
p = momentum vector
m = mass
v = velocity vector
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Momentum
• Momentum depends on the mass of an object and the speed it is going.– Momentum = mass x velocity
• Because velocity has direction then momentum does, also.
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Momentum of Objects
• Put the following in the order of most momentum to least:– Mosquito– Automobile– Space Shuttle– Bullet– Freight Train
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Questions
• Does a small object always have less momentum than a large one?
• How can a bullet from a rifle knock over an animal?
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Which has more momentum?
• A truck or a roller skate rolling down a hill with the same speed?
• A truck stopped at a light or a marble rolling down the road?
• When could the roller skate and the truck have the same momentum?
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What is Momentum?
An object with a lot of momentum is also hard to stop
Momentum = ρ = mv
Units: kg∙m/s
m=mass
v=velocity
Momentum is also a vector (it has direction)
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Momentum
Momentum is _________ in ________.
Momentum is a vector quantity.Momentum is dependant on the
mass and the ___________ of an object.
MASS
MOTION
VELOCITY
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Momentum Facts
• p = m v
• Momentum is a vector quantity!
• Velocity and momentum vectors point in the same direction.
• SI unit for momentum: kg · m /s (no special name).
• Momentum is a conserved quantity (this will be proven later).
• A net force is required to change a body’s momentum.
• Momentum is directly proportional to both mass and speed.
• Something big and slow could have the same momentum as something small and fast.
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Momentum Examples
10 kg 3 m /s
10 kg30 kg ·
m /s
Note: The momentum vector does not have to be drawn 10 times longer than the velocity vector, since only vectors of the same quantity can be compared in this way.
5 g
9 km /s
p = 45 kg · m /s at 26º N of E
26º
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Equivalent Momenta
Bus: m = 9000 kg; v = 16 m /s p = 1.44 ·105 kg · m /s
Train: m = 3.6 ·104 kg; v = 4 m /s p = 1.44 ·105 kg · m /s
Car: m = 1800 kg; v = 80 m /s p = 1.44 ·105 kg · m /s
continued on next slide
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Equivalent Momenta (cont.)
The train, bus, and car all have different masses and speeds, but their momenta are the same in magnitude. The massive train has a slow speed; the low-mass car has a great speed; and the bus has moderate mass and speed. Note: We can only say that the magnitudes of their momenta are equal since they’re aren’t moving in the same direction.
The difficulty in bringing each vehicle to rest--in terms of a combination of the force and time required--would be the same, since they each have the same momentum.
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April 19, 2023
Newton’s Law and Momentum
• Newton’s Second Law can be used to relate the momentum of an object to the resultant force acting on it
• The change in an object’s momentum divided by the elapsed time equals the constant net force acting on the object
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Problem A 1200 kg car drives west at 25 m/s for 3 hours.
What is the car’s momentum? Identify the variables:
1200 kg = m 25m/s, west = v 3 hours = t
p = mv
p = (1200kg)(25m/s) = 30000 kgm/s, west
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Homework
• Be ready with your procedure for next class.
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Leading to Inquiry for Total Momentum of a System Before and After a Collision or explosion
Each group will have a different type of collision or explosion. Some will overlap since we will focus on three types of collisions/explosions.
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© 2001-2007 Shannon W. Helzer. All Rights Reserved.
Momentum – Elastic Collisions period 5 start here
Elastic Collision – a collision in which the colliding bodies do not stick together.
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© 2001-2007 Shannon W. Helzer. All Rights Reserved.
Momentum – Inelastic Collisions
Inelastic Collision – a collision in which the colliding bodies stick together.
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Explosions“before”M
“after”m1
m2v1
v2
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© 2001-2007 Shannon W. Helzer. All Rights Reserved.
Momentum
Identify the number and types of collisions in the animation below.
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© 2001-2007 Shannon W. Helzer. All Rights Reserved.
Momentum
Identify the number and types of collisions in the animation below.
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© 2001-2007 Shannon W. Helzer. All Rights Reserved.
Momentum
Identify the number and types of collisions in the animation below.
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Inquiry for Total Momentum Before and After a Collision/Explosion
• PROBLEM• Design an experiment to demonstrate the
effect of a collision/explosion on total momentum of the objects before and after using the same mass for each cart and then for a second experiment change one of the cart’s mass by adding mass.
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Inquiry for Total Momentum Before and After a Collision/Explosion
• Design an experiment to demonstrate the effect of a collision/explosion on total momentum of the objects before and after using the same mass for each cart and then for a second experiment change one of the cart’s mass by adding mass to it.
• Make a prediction on the effect of some condition on the total momentum before and after a collision.
• Materials– Dynamics cart with spring bumper or plunger– Meter stick– Stop watch– Masses– Large white boards– Ramp
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Inquiry for Total Momentum Before and After a Collision/Explosion
• Your group will present using the whiteboards your design and findings.
• What did you discover about the momentum before and after a collision or explosion?
• What happened to the momentum before and after when one of the carts had more mass?
• Were any of the results NOT what you expected?• Did the data support your original prediction?
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Evaluation• Individually, you will write an analysis about the investigation
with supporting evidence, and then explain how the conservation of momentum can be applied to the investigation.
• Describe the investigation and the theoretical concepts related to the investigation.
• Can you test the predictions? What conclusion(s) did you reach due to the results of this experiment? If so, do results agree with your conclusion(s)?
• What evidence (text and/or data) supports your conclusion(s)?• Are your results reliable? What were the sources of error and
how did you compensate for sources of error in the experiment?
• This will be due 3 days after the conclusion of the investigations.
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Conclusions
• Based on the investigations, what conclusion can you make about the momentum in a system?
• Kahoot