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MOMENTUM
mass in motion
MOMENTUM (p)
p = mv
UNIT:
kg*m/s
Guess what…
That’s right!!
Momentum is a
vector!!
A 2250kg pickup truck
has a velocity of 25 m/s
to the east. What is the
momentum of the truck?
56000 kg*m/s East
A 1210kg pickup truck
has a momentum of
55000 kg*m/s to the
south. What is the
velocity of the truck?
45 m/s South
How can momentum
be changed?
A change in
momentum takes
force and time.
IMPULSE
In fact,
check it out:
nd
2
Newton’s
was originally
p
F
t
IMPULSE-MOMENTUM
THEOREM
Ft = p
(impulse = change
in momentum)
p = (mv)
•Change in velocity
•Change in mass
•Change in both
F is always
the Fnet
(aka SF)
A 1400kg car moving
westward with a velocity of
15 m/s collides with a pole
and is brought to rest in
0.30s. Find the magnitude
of the force exerted on the
car during the collision.
70000 N East
A 0.50kg object is at rest.
A 3.00 N force to the right
acts on the object during a
time interval of 1.50s.
What is the velocity of the
object after this time?
9.0 m/s to the right
A 0.40kg soccer ball approaches a
player horizontally with a velocity
of 18 m/s to the north. The player
strikes the ball and causes it to
move south with a velocity of 22
m/s. What impulse was delivered
to the ball by the player?
16 kg*m/s South
Momentum is
Conserved!!!
CONSERVATION OF
MOMENTUM
m1v1,i + m2v2,i = m1v1,f + m2v2,f
Initial Momentum = Final Momentum
A 76kg boater initially at rest
in a stationary 45 kg boat,
jumps out of the boat and
onto a dock. If the boater
jumps with a velocity of
2.5m/s to the right, what is the
final velocity of the boat?
4.2 m/s to the left
A 25 kg car moving to the
right at 5.5 m/s collides with a
35 kg car moving to the right
at 2 m/s. After the collision,
the the 25 kg car slows to 1.4
m/s to the right. What is the
velocity of the 35 kg car after
the collision?
5 m/s to the right
A 3500 kg truck going 25 m/s
East runs into a 550 kg
motorcycle stopped at a stop
sign. If the truck stops as a
result of the collision, how fast
will the motorcycle shove
forward?
160 m/s East
3 Types of Collisions
•Inelastic Collisions
•Perfectly Elastic Collisions
•Imperfect Elastic Collisions
Inelastic Collisions
The objects stick together
after they collide
(loss of KE)
m1v1,i + m2v2,i = (m1 + m2)vf
Perfectly Elastic Collisions
The objects bounce off
of each other
(no KE loss)
Same momentum eqn.
Imperfect Elastic Collisions
The objects bounce
off but lose KE
(elastic, sound, etc)