momentum, impulse, and collisions · with a momentum of 16 kg m/s east and it hits a 1.5 kg bowling...
Post on 05-Nov-2019
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Momentum
Momentum ( റ𝑝) is the product of mass and velocity
Momentum is a vector. It has a direction, so + and – signs matter.
Used to analyze collisions
Units: 𝑘𝑔∙𝑚
𝑠
റ𝑝 = 𝑚 റ𝑣
ExampleAn 80 kg running back is running 6 m/s and a 90 kg linebacker is running 5 m/s.
Which has more momentum?
a) The running back
b) The linebacker
c) They are the same
Which has more inertia?
a) The running back
b) The linebacker
c) They are the same
ExampleAn 80 kg running back is running 6 m/s and a 90 kg linebacker is running 5 m/s.
Which has more momentum?
a) The running back
b) The linebacker
c) They are the same
Which has more inertia?
a) The running back
b) The linebacker
c) They are the same
Impulse
Defined as the change in
momentum (∆ റ𝑝)
Defined as the product of
force and time ( റ𝐹𝑡)
Units: either 𝑁 ∙ 𝑠 OR 𝑘𝑔∙𝑚
𝑠
∆ റ𝑝 = റ𝐹𝑡
ExampleIn the diagram, a 60-kilogram roller skater exerts a 10-newton force on a 30-kilogram roller skater for 0.20 second. What is the magnitude of the impulse applied to the 30-kilogram roller skater? What about Newton’s 3rd law?
a) 50 N∙s
b) 2.0 N∙s
c) 6.0 N∙s
d) 12 N∙s
ExampleIn the diagram, a 60-kilogram roller skater exerts a 10-newton force on a 30-kilogram roller skater for 0.20 second. What is the magnitude of the impulse applied to the 30-kilogram roller skater? What about Newton’s 3rd law?
a) 50 N∙s
b) 2.0 N∙s
c) 6.0 N∙s
d) 12 N∙s
Example
An 8.0 kg bowling ball is rolling along
with a momentum of 16 kgm/s East
and it hits a 1.5 kg bowling pin, slows
down, and continues rolling with
10 kgm/s East. What is the magnitude
of the impulse delivered to the ball?
a) 2 kgm/s
b) 6 kgm/s
c) 8 kgm/s
d) 26 kgm/s
Example
An 8.0 kg bowling ball is rolling along
with a momentum of 16 kgm/s East
and it hits a 1.5 kg bowling pin, slows
down, and continues rolling with
10 kgm/s East. What is the magnitude
of the impulse delivered to the ball?
a) 2 kgm/s
b) 6 kgm/s
c) 8 kgm/s
d) 26 kgm/s
Example
A bumper car is sliding along with a
momentum of 700 kgm/s East,
collides with the wall, and bounces
back going 200 kgm/s West. What
was the magnitude of the impulse
delivered to the bumper car?
a) 500 kgm/s East
b) 500 kgm/s West
c) 900 kgm/s East
d) 900 kgm/s West
Example
A bumper car is sliding along with a
momentum of 700 kgm/s East,
collides with the wall, and bounces
back going 200 kgm/s West. What
was the magnitude of the impulse
delivered to the bumper car?
a) 500 kgm/s East
b) 500 kgm/s West
c) 900 kgm/s East
d) 900 kgm/s West
Example
A 0.046 kg golf ball that is initially at rest,
is struck by a golf club. The impact lasts
0.00018 s and the ball left the club going
78 m/s East.
What is the impulse delivered to the ball?
What was the average force applied to
the ball?
∆ റ𝑝 = റ𝐹𝑡
Example
A 0.046 kg golf ball that is initially at rest,
is struck by a golf club. The impact lasts
0.00018 s and the ball left the club going
78 m/s East.
What is the impulse delivered to the ball?
What was the average force applied to
the ball?
∆ റ𝑝 = റ𝐹𝑡
Example
A person’s head of 5.0 kg is moving
25 m/s East when it collides with an
airbag and comes to a stop. The
collision with the airbag is 0.08 s.
What is the impulse delivered to the
person’s head?
What is the average force applied to
the person’s head?
∆ റ𝑝 = റ𝐹𝑡
Example
A person’s head of 5.0 kg is moving
25 m/s East when it collides with an
airbag and comes to a stop. The
collision with the airbag is 0.08 s.
What is the impulse delivered to the
person’s head?
What is the average force applied to
the person’s head?
∆ റ𝑝 = റ𝐹𝑡
Impulse and airbags
If an object comes to a stop, the
impulse is fixed, but it can stop over a
short time OR a long time.
An airbag will extend the time of the
collision so that the average force
delivered to person’s head decreases.
∆ റ𝑝 = റ𝐹𝑡
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