Bellringer
 Pick up exam (Both Parts)
Objectives
 Make observations about momentum and
figure out what factors effect it.
 Test average: 77%
 Last year was an 84!
What is momentum?
 Momentum is mass times velocity:
 p = momentum
 m = mass
 v = velocity
If all three boats
were moving at the
same velocity
which would be
easier to stop?
Why?
Demonstrations
 Grab a sheet of paper to record your
observation.
Which would have more momentum,
A linebacker at full sprint or at rest?
Bellringer
 What is the momentum of a 75kg baby
crawling at 15m/s?
 Include units!
Objectives
 Complete collision lab.
If all three boats
were moving at the
same velocity
which would be
easier to stop?
Why?
Bellringer
 What is the momentum of a racecar
that is traveling at 30m/s and has a
mass of 1,000kg?
 30,000kg(m/s) or 30,000N*s
Objectives
 Understand how to use momentum
conservation to solve problems.
 Practice applying this knowledge to help you
solve problems.
Lab
 Due tomorrow
 Only need to show one example calculation for each
type of calculation.
What is momentum?
 Momentum is mass times velocity:
 p = momentum
 m = mass
 v = velocity
Example
 If you have a mass of 62 kg and you are running at a
constant velocity of 8 m/s what is your momentum
 If your car has a mass of 2000kg and is parked what is
it’s momentum?
Total Momentum
 The total momentum of a system can be found by
adding the momentum of each part of the system
together?
 Just like how we added all the forces on a system
together to find the net force
Total Momentum

Conservation of Momentum
 If two objects, that are not subjected to any
external forces, interact, the total momentum of
the objects before the interaction is equal to the
total momentum after the interaction.
pbefore = pafter
pAi + pBi = pAf + pBf
mAvAi + mBvBi = mAvAf + mBvBf
Is Momentum Always Conserved?
 Is momentum conserved when a car crashes into a
wall?
 Why?
Elastic and Inelastic collisions
 Elastic Collision: When two or more objects collide
and momentum is conserved.
 i.e. Atoms scattering
 Inelastic Collision: When two or more objects collide
and momentum is not conserved.
 i.e. Car crash
Elastic and Inelastic Collisions
 Most collisions are inelastic because some energy is
lost to some type of friction (sound, heat, etc.)
 We can treat some problems as elastic collisions to
make it easier to solve problems that deal with
momentum.
Checkpoint
1.
Are inelastic or elastic collisions more common in
real life? Why?
2. Are inelastic or elastic collisions more common in
our little physics world? Why?
Exploding Carts - Lab

Conservation of Momentum
 A 90 kg running back is running up field with a
constant velocity of 7 m/s. A 105 kg linebacker is
running down field with a velocity of 6.5 m/s as he
tackles the running back. After they collide find their
total velocity.
pbefore = pafter
pRi + pLi = pRf + pLf
mRvRi + mLvLi = mRvRf + mLvf
Conservation of Momentum
 Can you figure out the final velocity of the running
back if the linebacker doesn’t make the tackle?
 What would we need to know?
 What would be the running back’s final velocity if the
linebacker had a final velocity of 3 m/s down field.
pbefore = pafter
pRi + pLi = pRf + pLf
mRvRi + mLvLi = mRvRf + mLvLf
Collected

Collected!
A 5.0 kg gun fires a 0.0020 kg
bullet. If the bullet exits the gun at
800 m/s [east], calculate the recoil
velocity of the gun.
Homework
 Read pages 244 to 248 (Two-Particle
Collisions through Propulsion in
Space).
 Then answer problems 23, 24, and 25
on page 249
Bellringer
 A 3 kg gun fires a 0.0010 kg bullet. If
the bullet exits the gun at 500 m/s,
calculate the recoil velocity of the gun.
Objective
Solidify your understanding and
application skill of problems that
deal with the conservation of
momentum.
Explosion Lab
Physics Club Today
Physics Learning Center
 Thursday after school
 Now if you scored a 70 or below on the last exam
(without bonus) you must attend.
 I recommend that anyone who isn’t scoring above an
85 attends.
Momentum Practice Questions
 10 minutes
Momentum Videos
Momentum Practice Problems
Bellringer
 Pick up papers
 Take out and check your homework.
Objective
 Be able to solve conservation of momentum problems
 Begin to look into situations when momentum is not
conserved.
Textbook Practice Problems
 Textbook page 246
 17
 18
 19
 20
 21
Homework
 Read pages 244 to 248 (Two-Particle
Collisions through Propulsion in
Space).
 Then answer problems 23, 24, and 25
on page 249
Bellringer

Bellringer – 2 mins to hand in
 Take out your homework
and start to check it.
DO
STOP
WORK
Objective
Investigate situations where
momentum is NOT conserved.
Focus on how force and time
effect the change in momentum.
What do you know about momentum?
 So far we have
 And:
pbefore = pafter
 Is this all there is to know about momentum or is there
more for us to discover?
 Where should we start looking?
Momentum and Force
How does the force on an
object relate to its change in
momentum?
Crash Test Dummies
 Why do we have crash test dummies?
http://www.youtube.com/watch?v=8adfGDQ-uRA
Crash Test Dummies
 What is a car’s momentum before a collision with the
wall?
 What is a car’s momentum after a collision with the
wall?
 Is momentum of this system conserved?
Crash Test Dummies
 Where does all the initial momentum of the system
go?
Crash Test Dummies
 Does a crash test dummy experience a force as it
collides with something else?
 How do you know? Any evidence?
 How does this force relate to momentum?
Crash Test Dummy Checkpoint
 Does a larger force or a smaller force change the
momentum of a system more?
 Why?
Momentum and Time
How does the time of a
collision relate to the change
of momentum?
Tree Jumping
 Is it possible to jump out of a twenty foot tall tree
without hurting yourself?
 Is it possible to jump out of a twenty foot tall tree and
hurt yourself?
 Do both systems have the same change in
momentum?
Tree Jumping
 What can you change to make sure that you do not
hurt yourself as you jump out of a tree from 20 feet
above the ground?
 Parkour: The aim to move from one place to another,
negotiating the obstacles in between. The discipline
uses no equipment and is non-competitive, but still
extremely hardcore.
Video Clips
 http://www.youtube.com/watch?v=aAhPaiajwDY
 https://www.youtube.com/watch?v=0Kvw2BPKjz0
 What is the difference? Why do hardcore
parkour(ers?) not injure themselves when they fall
long distances? Does gravity effect them differently?
 The time of impact changes the force they feel.
The Change in Momentum is…?
 What is Newton’s Second Law? (Yup it’s back again)
 What is the equation for acceleration?
 Substitute.
 How can this be related to the change in momentum?
CANNONBALL!!!!!!!!!
 Use this new equation for the change in momentum to
explain how this man is able to pull of this remarkable
stunt.
 http://www.youtube.com/watch?v=lH45xpTASiw&list
=PL311480F303F33687&index=10
Egg Toss
 Are eggs easy to break?
Change in Momentum
What is the relationship or pattern
between force and time and how do
they both relate to the change in
momentum of a system?
Bellringer
 Fill out paper
 Next exam grade must be equal to or higher than your
last grade, and must be above a 70.
Objectives
 Practice solving problems using a brand new
equation.
 Solidify your understanding of how your
change in momentum can be a life or death
situation.
Exam
 This Friday
 Science Learning Center
 Thursday after school. 70 or below
 Any other time we’re both free
 Physics Club
 Tuesday after school.
 Finish application
 Test GPS
Homework
 Read “What about corked bats?”
 Write a solid argument about whether or not you
believe that a cork bat is easier to hit a baseball with.
Make sure to use information from the reading. This
will be discussed and collected tomorrow.
Momentum Review
 Five regents physics review questions
 5 minutes
 Solo
 3 minutes
 Partner
Impulse
 The impulse of a collision is the change in momentum
of the collision.
 The change in momentum is equal to the force during
the collision multiplied by the time of the collision.
 Or…
Impulse
 http://www.yout ube.com/watch?v=7RSUjxiZnME
 Why doesn’t the egg always survive if it always
experiences the same impulse?
 What happens to the impulse if an object experiences
the same force for a shorter amount of time?
 What happens to the impulse if an object a greater
force for the same amount of time?
Example
 A 65kg cross country runner is lined up at
the starting line. The official shoots the gun
to start the race. The runner exerts a
constant horizontal force of 200N on the
ground for 3 seconds.
 What is the runner’s impulse?
 What is the runner’s velocity?
Runner
 𝐽 = 𝐹𝑛𝑒𝑡 𝑡
 𝐽 = 200𝑁 ∗ 3𝑠
 𝐽 = 600𝑁 ∗ 𝑠 𝑜𝑟
𝑚
600𝑘𝑔
𝑠
 𝐽 = ∆𝑝
 𝐽 = 𝑝𝑓 − 𝑝𝑖
 𝐽 = 𝑚𝑣𝑓 − 𝑚𝑣𝑖

𝑚
600𝑘𝑔
𝑠
 𝑣𝑓 =
= 65𝑘𝑔𝑣𝑓 −
𝑚
9.23
𝑠
𝑚
0𝑘𝑔
𝑠
Practice
 A 500kg car is driving at constant velocity and then
hits a wall and comes to rest. The car experiences a
10,000N force for 0.5 seconds.
 What is the impulse experienced by the car?
 What was the initial velocity of the car?
Car Crash
 𝐽 = 𝐹𝑛𝑒𝑡 𝑡
 𝐽 = 10,000𝑁 ∗ 0.5𝑠
 𝐽 = 5,000𝑁 ∗ 𝑠 𝑜𝑟
𝑚
5,000𝑘𝑔
𝑠
 𝐽 = ∆𝑝
 𝐽 = 𝑝𝑓 − 𝑝𝑖
 𝐽 = 𝑚𝑣𝑓 − 𝑚𝑣𝑖
𝑚
=
𝑠
𝑚
−10
𝑠
 5,000𝑘𝑔
 𝑣𝑖 =
0𝑘𝑔
𝑚
𝑠
− 500𝑘𝑔𝑣𝑖
Bellringer
 Take out your homework
Objectives
 Master impulse problems
 Finish station problems
Physics
 Learning Center on Thursday
 70 or below
 Physics Club
 Finish application
 Test GPS
Impulse side
Stations
Bellringer
 What is a person’s change in momentum if they have a
mass of 75kg and are driving at 30m/s then come to a
stop.
 Is this person injured after they stop? Explain
Objective
 Master Impulse and Momentum
Friday’s Test
 10 Multiple Choice
 3 Long Answers
 1 Bonus
 8 Station Problems
 Multiple Choice Questions
 Textbook problems.
Happy and Sad Balls
 Which one has the greatest change in
momentum and why?
Impulse Practice Problems
Bellringer
 Cart A has a mass of 25kg and an initial velocity of
10m/s before it hits cart B, which has a mass of 10kg
and an initial velocity of 5m/s. If cart A has a final
velocity of just 7m/s, what is the final velocity of cart
B?
Air Track
Head on collision
 Why is it safer to be in the more massive car during a
head on collision?
Trains!
 https://www.youtube.com/watch?v=dzoHx29pkbI
 https://www.youtube.com/watch?v=UNmt13Y870U
 https://www.youtube.com/watch?v=1mHtOW-OBO4
 https://www.youtube.com/watch?v=5WcKIgrRlj8
 https://www.youtube.com/watch?v=vRfbL6memSs
Readings
Grade Slips
Last Lab
Lab Time