BELL RINGER 12/8:
Summarize what you did in Tuesday’s collision
activity.
OBJECTIVE: SWBAT define
conservation of momentum;
SWBAT define and calculate for
inelastic
AGENDA:collisions
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Notes
Group Practice
Exit Ticket
HOMEWORK: 1-5, 7-8a on Worksheet
Conservation of
Momentum
• Momentum in a system is conserved
• Pfinal=Pinitial
• In general, for two objects that are
colliding, the equation looks like:
initial m1v1 + m2v2 = m1v1 + m2v2
final
But, the equation is rearranged or changes
slightly depending on the type of
collision!
Applying conservation of
momentum
EX: Two ice skaters meet in the center of
the rink and come to rest. They now push
off against one another. One skater, with
a mass of 54-kg, acquires a speed of 0.95
m/s. What is the speed of the other
skater, whose mass is 61-kg?
Conservation of
Momentum + Collisions
• Momentum in the system (objects
colliding) is conserved as long as there
are no external forces acting on the
system
• That doesn’t mean momentums within
the system don’t change; the sum
remains the same, but momentum will
transfer b/w objects
COLLISIONS
There are two types of collisions:
1. Inelastic: momentum is conserved, but
kinetic energy is not; objects stick
together upon collision. When the
maximum amount of KE is lost to other
forms of energy, it is called a completely
inelastic collision.
2. Elastic: momentum and kinetic energy
are conserved
INELASTIC COLLISIONS
Note:
When one object starts at rest and the
one
objects stick together after the collision
and
object
won’t is
have the same final velocity, the equation
always
rearranged to:
start at
rest, so
m1v1 + m2v2 = m1v1 + m2v2
the m2v2
term can
come
m1v1 = (m1 + m2) v
back!
INELASTIC COLLISIONS
EX: On a touchdown attempt, a
95.0-kg running back runs to the right
towards the end zone at 3.75 m/s. An
111-kg linebacker moving to the left
at 4.10 m/s meets the runner in a
head-on collision. If the two players
stick together, what is their velocity
immediately after the collision?
12/5:
Answer Choices forEMI
Question
STANDARD:
6014:
OBJECTIVE: SWBAT solve collision
problems using the conservation of
energy
equations
AGENDA:
•
•
Group Practice
Start Problem Set
HOMEWORK: Problem Set due
Monday (check your email); QUIZ
MONDAY!
12/5:
What is the general equation for
conservation of momentum?
OBJECTIVE: SWBAT solve collision
problems using the conservation of
energy
equations
AGENDA:
•
•
Group Practice
Start Problem Set
HOMEWORK: Problem Set due
Monday (check your email); QUIZ
REVIEW
A train with a mass of 3500-kg is
traveling at 20 m/s when it
collides with another train that
has a mass of 2700-kg and is
traveling 15 m/s. If the objects
stick together upon collision,
what will be the trains’ velocity
right after colliding?
GROUP PRACTICE