Transcript Chapter 9 Momentum - Mrs. Krusa`s Wikispace

Chapter 9
Momentum
Is equal to the mass of an object times
the velocity of an object
Has the symbol “p”
so
p= m • v
- measured in kg•m/s
- It is a vector quantity
Momentum and Impulse
Connection
F=m a= m (v/t)
F= m (v/t)
Ft= m v
Impulse= change in momentum
or
Impulse= pf-pi
Con.
Impulse(J)= F•t= m•v
This is known as the impulse-momentum
change equation
3 Major Truths
1. The impulse experienced by an object is the
force • time.
2. The momentum change of an object is the
mass•velocity change.
3. The impulse equals the momentum change.
http://www.glenbrook.k12.il.us/gbssci/phys/Cla
Example
A 2200-kg car traveling at 26 m/s can be
stopped in 21 s by gently applying the
brakes. It can be stopped in 3.8 s if the
driver slams on the brakes, or in .22 s if
it hits a concrete wall. What average
force is exerted on the car in each of
these stops?
Videos of Safety built into Cars
http://www.youtube.com/watch?v=kzq
PwrvOwYI
Law of Conservation of
Momentum
The momentum of any closed, isolated
system does not change
pi = p f
Two Particle Inelastic Collision
A 1875kg Escalade going 23 m/s rear-ends a
1025 kg Cobalt going 17 m/s on ice in the
same direction. The two cars stick together.
How fast do the two cars move together
immediately after the collision?
Inelastic collision- two colliding objects stick
together and move with the same final
velocity
Elastic collision- two colliding objects bounce off
each other
Example of Recoil
Luke was studying his Physics while at practice.
As he was standing in the middle of the rink,
he decides to throw his book at Erik as he is
skating by. He was totally amazed at the
Physics law he just demonstrated. If the mass
of the book is 2 kg and Luke’s mass is 77 kg,
what is Luke’s velocity after he throws the
book at 2 m/s? How long does it take Luke
to reach the edge of the rink if the diameter
of the rink is 10 meters?
Example of Propulsion in
Space
An astronaut at rest in space fires a
thruster pistol that expels 35 g of hot
gas at 875 m/s. The combined mass of
the astronaut and pistol is 84 kg. How
fast and in what direction is the
astronaut moving after firing the pistol?
Examples of Two-Dimensional
Collisions
Example #1
A 1325 kg Cavalier moving north at 27.0
m/s, collides with a 2165 kg Lincoln
moving east at 11.0 m/s. The two cars
are stuck together. In what direction
and with what speed do they move
after the collision?
Example # 2
A stationary billiard ball, with a mass of
0.17 kg, is struck by an identical ball
moving at 4.0 m/s. After the collision,
the second ball moves 60.0° to the left
of its original direction. The stationary
ball moves 30.0° to the right of the
moving ball/s original direction. What is
the velocity of each ball after the
collision?