Momentum
SC.912.P.12.5
• Apply the law of conservation of linear momentum
to interactions, such as collisions between objects.
• Define the concept of momentum.
• Explain how momentum is conserved in a collision
between objects.
• SC.912.P.12.6
• Qualitatively apply the concept of angular
momentum .
• Describe with words or with diagrams the
momentums and velocities involved with an object
traveling in a circular path.
• Define angular momentum.
Momentum Scale
4
• Experiment using materials that would use the law of
conservation of momentum to increase safety features
of various motor vehicles. (SC.912.12.5)
3 - MPT Learning Goals
• Apply the law of conservation of linear momentum to
interactions, such as collisions between objects.
(SC.912.12.5)
• Qualitatively apply the concept of angular momentum
(SC.912.P.12.6)
2
• Illustrate situations describing the law of
conservation of momentum in action.
(SC.912.12.5)
• describe why an object traveling in a circular path
is exhibiting angular momentum. (SC.912.P.12.6)
1
• State the law of conservation of momentum.
(SC.912.12.5)
Vocabulary words
• Momentum
• Angular
momentum
• Law of
conservation of
linear momentum
• Scalar
• Vector
•
•
•
•
•
Projectile
Rotation
Parabola
Trajectory
Velocity
Vocabulary
• Momentum – is mean inertia in motion. More
specifically, momentum is the mass of an
object multiplied by its velocity.
• momentum = mass x velocity
momentum = mass x speed (When direction
is not an important factor)
It refers to the quantity of motion that an object
has.
A moving object can have a large momentum if it
has a large mass, a high speed, or both.
• Law of conservation of momentum states that,
in the absence of an external force, the
momentum of a system remains unchanged.
If a system undergoes changes wherein all forces
are internal as for example in atomic nuclei
undergoing radioactive decay, cars colliding, or
stars exploding, the net momentum of the system
before and after the event is the same.
• Angular momentum - is a property of
objects which are not only changing their
position but also the direction of their
position with respect to a reference
point(they are not moving in a straight line).
• Lineal momentum- is a property of an
object which is in motion with respect to a
reference point (any object changing its
position with respect to the reference
point).
• Scalars are quantities that are fully described by a
magnitude (or numerical value) alone. (5 m, 20
degrees Celsius, 256 bytes, 4000 Calories)
• Vectors are quantities that are fully described by
both a magnitude and a direction. (30 m/sec,
East, 5 mi. North)
• Magnitude - refers to size or quantity
alone. When it comes to movement, magnitude
refers to the speed at which an object is traveling
or its size.
• Projectile is an object upon which the only force
acting is gravity.
• Projectile motion is a form of motion in which
an object or particle (called a projectile) is
thrown near the earth's surface, and it moves
along a curved path under the action of gravity
only.
• The only force of significance that acts on the
object is gravity, which acts downward to cause
a downward acceleration.
• A projectile is any object that once
projected or dropped continues in motion by
its own inertia and is influenced only by the
downward force of gravity.
• Rotation
• Parabola
• Trajectory
A truck rolling down a hill has more
momentum than a roller skate with the same
speed. But if the truck is at rest and the roller
skate moves, then the skate has more
momentum.
Newton's Cradle demonstrates the principle of
the conservation of momentum
• When the balls on one
side are lifted and
released so they make
contact with the others,
the momentum of balls
is the same before and
after the collision—the
same number of balls
emerge at the same
speed on the other
side.
How does Newton's Cradle work?
• When the first ball of Newton's
• How does Newton's Cradle
Cradle collides with the second,
work?
the first ball stops, but
• When a ball on one end of the
its momentum isn't lost, just
cradle is pulled away from the
transferred to the second ball,
others and then released, it
then the third, then the fourth,
strikes the next ball in the
until it reaches the very last ball.
cradle, which remains
You witness this conservation of
momentum as the last ball
motionless. But the ball on the
swings into the air with nearly
opposite end of the row is
the same momentum as the first
thrown into the air, then
ball. If two balls are lifted into
swings back to strike the other
the air on one end of the device
balls, starting the chain
and released, then two balls on
reaction again in reverse.
the opposite end will swing in
response.
Activity: Collisions of Marbles
MATERIALS: five marbles, ruler
How Does a Collision Affect the Motion of Marbles?
• 1. Place five marbles, all identical in size and shape, in the
center groove of a ruler. Launch a sixth marble toward the
five stationary marbles. Note any changes in the marbles’
motion.
• 2. Now launch two marbles at four stationary marbles.
Then launch three marbles at three stationary marbles,
and so on. Note any changes in the marbles’ motion.
• 3. Remove all but two marbles from the groove. Roll these
two marbles at each other with equal speeds. Note any
changes in the marbles’ motion.
Analyze and Conclude
• Observing: How did the approximate speed of
the marbles before each collision compare to
after each collision?
• Drawing Conclusions: What factors determine
how the speed of the marbles changes in a
collision?
• Predicting: What do you think would happen if
three marbles rolling to the right and two
marbles rolling to the left with the same speed
were to collide?
EXPECTED OUTCOME:
• When a marble or marbles collide with the marbles at
rest, the momentum is the same before and after the
collision. As a result, the same number of marbles
emerges at the same speed on the other side.
ANALYZE AND CONCLUDE:
• 1. When one marble collides with 5 marbles, the
colliding marble stops and one marble emerges at the
same speed on the other side. When 2 marbles collide
with 4 marbles, 2 marbles emerge at the same speed.
The pattern continues with more marbles.
• 2. The speed and number of marbles.
• 3. Three marbles move to the right and two marbles
move to the left.
Summary
• Momentum…
– is a quantity that describes an object's resistance
to stopping (a kind of "moving inertia").
– is represented by the symbol p (boldface).
– is the product of an object's mass and velocity.
p = mv
– is a vector quantity (since velocity is a vector and
mass is a scalar).