Transcript Momentum and Impulse notes

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EQ: How are Momentum and Impulse
expressed, and what factors contribute to
momentum and impulse?
LO: We will investigate the components of
momentum and impulse and apply them to
solve word problems.
CT: I will summarize the formula for
momentum and impulse in words, and do
practice problems calculating momentum
and impulse.
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Mass in motion
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Momentum is directly proportional
to an object's mass and directly
proportional to the object's velocity.
p~m
and
p~v
Equation:
Momentum = mass x velocity
P = mv
Quantity
Variable
Unit
Momentum
p
kg*m/s
Mass
m
kg
Velocity
v
m/s
 Huge ship moving at a small velocity
P = Mv
 High velocity bullet
P = mv
Now complete 1-7 on your worksheet
(3 min)
The world’s most massive train ran in
South Africa in 1989. Over 7 km long, the
train traveled 861.0 km in 22.67 h. Imagine
that the distance was traveled in a straight
line north. If the train’s average
momentum was 7.32 x 108 kg•m/s to the
north, what was its mass?
hints: convert distance
convert time
manipulate equation
1.
The world’s most massive train ran in South Africa in 1989. Over 7 km long, the train traveled 861.0 km in
22.67 h. Imagine that the distance was traveled in a straight line north. If the train’s average momentum
was 7.32 x 108 kg•m/s to the north, what was its mass?
2.
One of the smallest planes ever flown was
the Bumble Bee II, which had a mass of
1.80 × 102 kg. If the pilot’s mass was
7.0×101 kg, what was the velocity of both
plane and pilot if their momentum was
2.08×104 kg•m/s to the west?
hints: use the total mass of both the
plane and the pilot.
manipulate the equation
What factors determine momentum?
How do these factors affect each other?
Write a sentence in which you include the
word momentum.
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Impulse -amount of force needed to stop an
object’s momentum in a specific amount of
time. Units N·s
I = FΔt
Quantity
Impulse
Force
Time
Variable
I
F
t
Unit
N·s
N
s
https://www.youtube.com/watch?v=s6QR0KdyTFY&feature=relmfu
What does momentum and impulse have to do with
each other?
Momentum = mv
If velocity changes, momentum changes, and acceleration (either + or –)
occurs
But we know:
1. for acceleration to occur, a force has to be applied.
2. If a given force is applied over a longer time, more acceleration occurs.
IMPULSE is a measure of how much force is applied for how much
time, and it’s equal to the change in momentum.
Impulse = Force x time
A force applied over time will change the momentum of an object:
FΔt = Dp
Impulse = Change in momentum
Newton’s Second Law can read
F = ma
 Dv 
F  m 
 Dt 
m Dv
F
Dt
Dp
F
Dt
FΔt = Dp  FΔt = pf –pi  FDt = mvf-mvi
Impulse = Change in momentum
If the boxer moves away from the punch, he extends the
time and decreases the force while stopping the punch.
If he moves toward the punch, he decreases the time
and increases the force
The airbag extends the time over which the impulse is
exerted and decreases the force.
Hitting the bricks with a sharp karate blow very
quickly maximizes the force exerted on the bricks
and helps to break them.
 Increase Dt and minimize the
force
 Catching a ball
 Bungee jumping
 Air bags
 Seat bealts
Dt
F
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Momentum is mass
in motion
P = mv
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Impulse is how
much force is
applied for a given
time on an object
I = FΔt
Putting it altogether:
The amount of force
applied over a given time
changes the object’s
momentum
FΔt = Dp