Download Momentum and Impulse

Bellwork
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Why don’t you want your egg to
bounce for the project?
Because, it may hit the hard ground
and crack / break.
Today’s Agenda
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Follow-up on this week’s lab
Momentum and Impulse notes
Egg Drop Analysis
Momentum and Impulse and the Egg
Drop
Sports Figures Video
Next homework assignment
Work and Power Lab
Follow-Up
1/10/14
Follow-up Questions
(in your notes)
1. How can a large force result in
relatively small power?
2. How can a small force result in
relatively large power?
Follow-up Questions
(in your notes)
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[Combining Work and Power equations]
Follow-up Questions
(in your notes)
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Force and distance are directly
proportional to power
Time is indirectly proportional to
power
Follow-up Answers
(in your notes)
1. If the force is done over small
distances and/or a long period of
time
2. If the force is done over large
distances and/ or a short period of
time
Follow-up Answers with values
1. Example: F = 5500 N; d = 0.015 m and
t = 3600 s is…
P = 0.023 W
2. Example: F = 5.5 N; d = 1500 m and
t = 0.36 s is…
P = 23,000 W
Momentum and Impulse
Notes
1/10/14
Pre-Quiz
(8 True/False Questions)
1. Impulses are normally smaller when
bouncing takes place.
2. If a net force acts on an object, the
object's momentum will change.
3. Momentum is defined as an object's
mass times its velocity.
4. If the net external force acting on a
system is zero, then the total momentum
of the system is zero.
Pre-Quiz
5. Impulse is defined as the force exerted on
an object times the time it lasts.
6. Automobile seatbelts are used to lengthen
the time of impact in case of a collision.
7. When a baseball player follows through
when hitting the ball, the contact time with
the ball is longer.
8. The momentum of a large truck at rest is
greater then the momentum of bee flying
across the room.
Pre-Quiz Answers
1. Impulses are normally smaller when
bouncing takes place. FALSE
2. If a net force acts on an object, the
object's momentum will change. TRUE
3. Momentum is defined as an object's
mass times its velocity. TRUE
4. If the net external force acting on a
system is zero, then the total momentum
of the system is zero. FALSE
Pre-Quiz Answers
5. Impulse is defined as the force exerted on an
object times the time it lasts. TRUE
6. Automobile seatbelts are used to lengthen the
time of impact in case of a collision. TRUE
7. When a baseball player follows through when
hitting the ball, the contact time with the ball is
longer. TRUE
8. The momentum of a large truck at rest is
greater then the momentum of bee flying
across the room. FALSE
Momentum and Impulse
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Momentum (vector): An object that is
in motion
Unit: kg · (m/s)
Impulse (vector): The time and
amount of force acting on an object
Unit: N · s
Momentum and Impulse
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Impulses change the momentum of
objects
The longer the force acts on an object
the greater the momentum change
(following through on a swing)
Extending impact times decreases the
force (air bags and seat belts)
Momentum and Impulse
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In a collision, an object experiences a
force for a given amount of time that
results in its mass undergoing a
change in velocity.
Impulse = change of momentum
F · t = Δ (m · v)
Egg Drop Analysis
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Individual – everyone needs to do the
analysis
Due Monday 1/27/14
Save an egg, crack a smile!
Oh no, Mr. Bill!
Momentum and Impulse and the
Egg Drop Project
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F · t = Δ (m · v)
You can not change the mass (m)
You can not change the velocity (v)
But you can try to change the time (t)
So, what will this do to the force (F)?
Egg vs. Tile Floor
F·
t
= Change of momentum
Egg vs. Grass
F
·
t = Change of momentum
Egg Drop Project
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F · t = Δ (m · v)
Your goal is to maximize the time!
F · = Change of momentum
· t = Change of momentum
t
F
Video
Homework
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IMPORTANT!!! If given the mass in kg
you need to find the weight (Fg) of the
object!
Work and Power Problems
Due Tues. 1/14/14