Due now:
Unit 4 HW 1
Get out a
colored pen!
Do Now:
1. Walk in silently.
2. Grab a calculator and any papers for today.
3.
A 1 kg ball is rolling across the floor with a velocity of
2m/s. You apply an impulse of 3 N*s.
What is its final velocity?
What is its final momentum?
Follow: ms_kellys_universe
Do Now:
1.
2.
3.
Due Next Class:
• U4.HW2
5 questions
Walk in silently.
Grab a calculator and any papers for today.
A 1 kg ball is rolling across the floor with a velocity of 2m/s.
You apply an impulse of 3 N*s.
What is its final velocity?
What is its final momentum?
SOI : Often times, as energy is
“used” and transformed from
one form to another we
endure some “loss” that can
be minimized to increase
sustainability in our world.
By the end of today, IWBAT…
- Apply the conservation of momentum
to solve problems.
Why it matters in LIFE:
Part of being a
functional human
being is being able to
understand what’s
happening in the world
around you!
Why it matters in THIS CLASS:
Our Goal = 80%
Mastering today’s lesson (focused
participation, asking questions, etc)
is the first brick that will help us
reach our goal for this unit, and
eventually for the year
TEKS:
6(C) calculate the mechanical
energy of, power generated
within, impulse applied to, and
momentum of a physical
system;
By the end of today, IWBAT…
- Apply the conservation of
momentum to solve problems.
Topic:
Conservation of
Linear Momentum
VOCAB CARDS
LIGHTNING
ROUND!
WHAT IT MIGHT LOOK LIKE ON A TEST:
DEMONSTRATION!
MOMENTUM, p (units - kg*m/s)
Momentum is “mass in motion”; it is the product of the
mass and velocity of an object. IT IS A VECTOR!
p = m(v)
p = momentum (kg* m/s)
m = mass (kg)
v = velocity (m/s)
CONSERVATION OF MOMENTUM
p1i + p2i = p1f + p2f
Before collision
After collision
m1v1i + m2v2i = m1v1f + m2v2f
ELASTIC COLLISIONS
The objects bounce off each other!
m1v1i + m2v2i
Before collision
=
m1v1f + m2v2f
After collision
EXAMPLE GP #1
A 0.014kg red bouncy ball is traveling at a velocity
of 1.2 m/s to the right. It collides elastically with a
initially stationary blue bouncy ball (mass of 0.011
kg). If the red ball has a final velocity of 0.5 m/s to
the left, what is the final velocity of the blue ball?
G: m1 = 0.014kg
v1i = 1.2 m/s
v1f = -0.5 m/s
m2 = 0.011 kg
v2i = 0 m/s
U: v2f =?
E: m1v1i + m2v2i = m1v1f + m2v2f
S: v2f = 2.16 m/s
CONSERVATION OF MOMENTUM
GUIDED PRACTICE!
Complete #2 on the GP with your partner!
INELASTIC COLLISIONS
Type 1: The objects stick together!
m1v1i + m2v2i
Before collision
=
m1v1f + m2v2f
=
(m1+m2) vf
After collision
EXAMPLE GP #3
A 1300kg car traveling at 26 m/s and a 1500kg
car that is traveling at 30 m/s are headed straight
for each other. They collide inelastically. What is
their final velocity?
G: m1 = 1300kg
v1i = 26 m/s
m2 = 1500 kg
v2i = -30 m/s
U: vf = ?
E: m1v1i + m2v2i = (m1 + m2)vf
S: v2f = - 4 m/s
CONSERVATION OF MOMENTUM
GUIDED PRACTICE!
Complete #4 on the GP with your partner!
Use the info from #2!
INELASTIC COLLISIONS
Type 2: The objects break apart!
m1v1i + m2v2i
(m1+m2) vi
Before collision
=
=
m1v1f + m2v2f
After collision
EXAMPLE GP #5
You (mass of 75 kg) are holding a pile of physics text
books (mass of 7kg) and standing on a skateboard
traveling at 4 m/s to the east. You throw the pile of
textbooks behind you (west) with a velocity of 1.5 m/s.
What is your final velocity?
G: m1 = 75 kg
m2 = 7 kg
vi = 4 m/s
v2f = -1.5 m/s
U: v1f =?
E: (m1+ m2)vi = m1v1f + m2v2f
S: v1f = 4.51 m/s
CONSERVATION OF MOMENTUM
GUIDED PRACTICE!
Complete #6 on the GP with your partner!
Use mass of the trains info from #2!
HOW DO I KNOW WHAT’S HAPPENING?
1. Look for key words:
Elastic, inelastic, stick together, break
apart, bounce off, separate...
2. Illustrate the problem to see what’s
happening.
INDEPENDENT PRACTICE!
Procedure for IP time:
1)
Silent work time
2) Try and solve without notes first!
Hierarchy of who to ask
1) Your brain
2) Your notes
3) Ms. Kelly (after you #embracethestruggle)
EXIT TICKET
You (mass 80kg) are skating at 7 m/s to the left toward
your friend. You friend (mass 75 kg) is skating at 8 m/s
to the right towards you.
1. If you collide elastically, your final velocity will be 4
m/s to the right. What is your friend’s final velocity?
2. If you collide inelastically, what will you and your
friend’s final velocity be?
EXIT TICKET
1. v2f = - 3.73 m/s
2. vf = 0.26 m/s
ON THE BACK OF YOUR E.T.
What was one thing you did really well today?
Where is one area where you can improve?
REMEMBER
Newton’s 3 rd Law – Every force has an equal
and opposite force.
F1 = -F2
And if the force takes place over time, like in a collision:
F1Δt = -F2 Δt
Apply the Impulse-Momentum Theorem:
m1Δv = -m2 Δv