1. Collisions
_________________ are a fact of life:
In _________: Hands, feet, heads, bats, rackets,
clubs, collide with balls, nets, goals, posts, people,
diving boards, etc. _________collide with each other.
__________ collide with other cars, buildings,
people, bicycles, etc.
__________ or parts of atoms collide with other
atoms. Light collides with ____________.
Planets, stars, and galaxies collide with
__________________.
sports
Players
Cars
Atoms
matter
each other
momentum (p = mv)
Physics uses ______________________ to study
collisions because it allows us to ignore the
___________ between the objects, which can be
very __________________ during a collision.
forces
complicated

3. A collection of objects that _____________ with
each other is called a ____________ of objects:
interact
system
boundary
SYSTEM
_________
forces:
internal 1 2 3
The total ______________ of a system of objects
will change if a net ____________ is applied to it:
momentum
impulse
impulse = change in momentum =
DpTotal J D
Fnett
(p1
+ p2
+ p3 + … )

5. But what if there is ________ impulse acting on the
system? This can only happen if the system is
________________, which means there is no net
____________ acting on it.
NO net
isolated
force
Any ___________ (outside)
force exerts _________
force on the system
“external”
no net
SYSTEM 1 2
The “system” exerts no
force, such as__________
on the “outside”
friction 3
No Fnet  no ____  no _____
 ptotal _____________________
Dptotal J
remains constant

7. The Law of Conservation of Linear Momentum:
The __________ momentum of an isolated
system of objects ____________________ . This
means that the total p _________ a collision (or an
explosion) equals the total p ________ the collision:
total
remains constant.
before
after
= (In ___________)
pbefore
pafter
PhysRT
If the “system” consists of 2 objects, this is written: =
p p2
p1' p2 '
m1v1' m2v2'
m1v m2v2
 the prime symbol: ' represents “_______”
after

8. helmet construction:

9. Ex 1: ___________ Collision. A 1.0-kg block and a 2.0-kg
block slide on a horizontal frictionless table as shown.
Elastic
v2 = 1.5 m/s
v1 = 6.0 m/s
2.0 kg
1.0 kg
The "system" consists of _____ blocks.
The system is "isolated," b/c there is no ___________. 2
friction
The two blocks collide and ____________ (exert forces on each other). After the collision, they move apart with the velocities shown below:
interact
v2 = ?
v1 = 4.0 m/s
2.0 kg
1.0 kg

11. Conservation of momentum says:
pbefore pafter
p p p1' p2'
m1v m2v m1v1' m2v2'
(1)(6) + (2)(-1.5) (1)(-4) (2)v2'
(Velocities have direction: left is_____________ )
v2'
v2'
v2'
v2'
3.5 m/s v2' =
negative
w/units:

13. Ex 2: ______________ Collision. A 4.0-kg block and a 2.0-kg
block slide on a horizontal frictionless table as shown below.
Inelastic
v1 = 0.75 m/s
v2 = 6.0 m/s
4.0 kg
2.0 kg
as one
After they collide, they ________________ and move ________.
What is the velocity of the "stuck together" mass?
stick together
v' = ?
4.0 kg
2.0 kg
Notice that the final v does not have _______________
1 or 2, because both masses ________________________
____________________ .
subscripts
have the same
final velocity

14. car deer
collisions:

15. Conservation of momentum says: pbefore pafter p1 + p2 p1' + p2'
m1v m2v m1v1' m2v2'
(4)(0.75) + (2)(-6.0)
v' v'
(The ______________ on _____ are dropped.) v' v'
-1.5 m/s v' =
(4)v1' (2)v2'
subscripts v'
combined
mass
w/units:
left
The combined mass moves to the ________ .

17. Ex 3: ___________ /Spring Release. A 3.6-kg mass
and a 1.2-kg mass are connected by a spring and
__________ on a horizontal frictionless table:
Explosion
at rest
v = 0
3.6 kg
1.2 kg
When the spring _______________ , the 3.6-kg mass
moves off to the left at the speed given. Determine
the speed of the 1.2-kg mass.
is released
v1 = 0.70 m/s
v2 = ???
3.6 kg
1.2 kg

19. Conservation of momentum says:
pbefore pafter
p p p1' p2'
m1v m2v m1v1' m2v2'
Both masses begin at rest  ________ for both.
v2'
v2'
v2'
v2'
2.1 m/s v2' =
(3.6)(0) + (1.2)(0)
(3.6)(-0.70) + (1.2)v2'
vi = 0
w/units:

20. Large Hadron Collider:

21. In this example:
The total momentum of the system _________
the spring is released equals ______ because both
masses begin _____________ .
The total momentum of the system ________
the spring is released equals ______ because of the
Law of ___________________ of Linear Momentum.
3. __________ mass receives a greater force b/c of
Newton's 3rd Law: ________ but ____________ forces.
The smaller mass moves ___________ because
acceleration a = F/m is _____________ proportional
to mass, and its mass is _____________ .
 It has ____ less mass, so it gains ____ more speed.
before
at rest
after
Conservation
Neither
Equal
opposite
faster
inversely
smaller 3x 3x

22. In sum: ________________ , is used in 3 cases: pbefore = pafter
1. _____________ (bouncing):
Elastic
2. _______________ (sticking):
Inelastic
v ____________
the same
_______________ mass
combined
3. ____________ /__________ release:
Explosion
spring
v = 0
still 0
total p = ____
total p = ___________

23. In Textbook:
page 219: # 1, 2 and 3a
page 224: # 1 and 4