impulse, momentum, and collisions. sections covered – physics – chapter 7: pages 86 – 99 –...
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![Page 1: Impulse, Momentum, and Collisions. Sections Covered – Physics – Chapter 7: pages 86 – 99 – *Chapter 10: pages136 - 146 Topics Covered – Linear Momentum](https://reader030.vdocuments.mx/reader030/viewer/2022032705/56649dc85503460f94abe666/html5/thumbnails/1.jpg)
Impulse, Momentum, and Collisions
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• Sections Covered – Physics– Chapter 7: pages 86 – 99– *Chapter 10: pages136 - 146
• Topics Covered– Linear Momentum– Impulse– Conservation of Momentum– Collisions
• Elastic• Inelastic• Total inelastic
– *Center of Mass
Impulse, Momentum, and Collisions
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• What is inertia?
*Review
How much resistance an object has against a change in motion.
Mass = numerical amount of inertia
Large mass = lots of resistance Small mass = not a lot of
resistance
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• Momentum is a quantity of movement or a measurement of how difficult it is to bring an object to a stop.
Momentum
Two Kinds of Momentum:
Linear Momentum-
Angular Momentum-
Momentum in a straight line
Rotational or Circular Momentum
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Linear Momentum p = linear momentum m = mass
SI Units:
v = velocity
Linear momentum is a vector that points in the same direction as the velocity.
v
p
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• A truck with a mass of 9000 kg moving 50 m/s?
Which Has More Momentum?
A moped with a mass of 180 kg moving 10 m/s?
OR
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• For a constant force, the product of the force and time over which the force acts is the Impulse
Impulse
J = Impulse F = force Δt = time of contactSI
Units: Impulse is a vector
with the same direction as the force applied.
F
J
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• The impulse exerted on an object changes the momentum of the object.
Impulse-Momentum Theory
The larger the impulse, the greater the change in momentum
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• When you fall a significant distance and hit the ground, why do they tell you to tuck and roll when you hit the ground rather than just landing right on your feet?
Conceptual Question
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Defining the System – Internal vs. External Forces
• Define your system (in this chapter – this will normally involve 2 objects)
The two skaters above are in a closed system
Any forces acting within your define system are internal forces
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Defining the System – Internal vs. External Forces
• Forces that act on an object outside of the defined system are called external forces
Examples:
◦ Case 2
◦ Case 1:
◦ Meteor = External Force. Outside of the system
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Defining the System – Internal vs. External Forces
• Forces that act on an object outside of the defined system are called external forces
Examples:
◦ Case 2
◦ Case 1:
◦ Meteor = External Force. Outside of the system
◦ Earthquake= External Force. Outside the system – changes how the problem is evaluated
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• The total momentum of an isolated or closed system remains constant.
Conservation of Momentum
Isolated/Closed Systems – systems with only internal forces, no external
Total Initial momentum = Total Final Momentum
Two Object Conservation of Momentum (For Objects 1 and 2):
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Conservation of Momentum
• For two objects, object A and object B:
Example:
A B
mA = 2.3 kg
vAo = 1.4 m/s
mB = 0.8 kg
vBo = 0 m/s
A B
vAf = 0.2 m/s vBf = ? m/s
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A tennis player places a 55.0 kg automatic ball machine on a virtually frictionless tennis court. Both the machine and tennis balls inside are initially at rest. The machine fires a 0.0570 kg tennis ball with a positive velocity. The machine moves backwards with a velocity of -0.0373 m/s. What is the velocity of the tennis ball?
What are the two objects in this system?
Warm-Up #1
vf = 36.0 m/s
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An ice skater (mass = 65.0 kg) moving to the right with a velocity of 2.50 m/s, holding a snowball (mass = 0.150 kg) which is moving with the skater. She then throws the snowball with a velocity of 32.0 m/s with respect to the ground. What is the velocity of the skater after she throws the snowball?• What are the two objects in this system?
Warm-Up #2
vf = 2.43 m/s
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A boy on a skateboard is initially at rest holding an 8.00 kg jug of water. He tosses the water, giving it a positive velocity of 3.00 m/s. The boy and skateboard move backwards with the magnitude of their velocity being 0.600 m/s. What is the mass of the boy and skateboard together? • What are the two objects in this system?
Warm-Up #3
m = 40.0 kg
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Collisions!!
• Three different kinds of collisions
IMPORTANT: In ALL collisions, momentum is conserved.
Elastic Collisions
Inelastic Collisions
Total Inelastic Collisions
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Elastic
Collisions!Inelastic Total
Inelastic Perfect rebound,
no energy loss
Momentum conserved
KE conserved KEo = KEf
Some energy loss
Momentum conserved
KE NOT conserved
Objects are stuck together after collision
Momentum conserved
KE NOT conserved
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Collision Kinetic Energy Conserved
Momentum Conserved
Elastic Collision
Inelastic Collision
Total Inelastic Collision
Collision Summary
YES YES
NO YES
NO YES