Momentum
“Joe Nathan has just struck
out 3 in a row! It looks like the
Twins have shifted the
momentum of this game.”
What does this mean?
All Day…..
“Make no mistake, Harrell ran
Peterson hard. He even told him
to line up eight yards behind the
line of scrimmage because he
got so much momentum so
quickly.”
http://espn.go.com/video/clip?id=7636553
The Vikings are doing some forensic accounting on Adrian
Peterson's rushing statistics, hoping to discover nine extra
yards in the couch cushions that would allow him to break Eric
Dickerson's 1984 single-season record of 2,105 yards.
“Momentum moving forward”
“Gaining momentum”
Keep with the plan.
One-direction…ahead.
Sports…advantage.
Favorable outcome?
Picking up speed
Things are happening!
Momentum
• As defined by Newton, it’s the product of
an object’s mass and velocity.
Bill – Momentum clip
Beakman
Which has more momentum?
22 caliber bullet
Mass = 30 grains (1 lb= 7000 grains)
1.9 grams
Speed = 1300 ft/s or 397 m/s
Seabourn Legend
Mass = 10,000 tons (1 ton = 2000 lbs)
9,090,909 kg
Speed = 16.5 knots (1 knot = 1.15 mph)
8.5 m/s
Speed 2 Clip
http://www.metacafe.com/watch/hl14415760/speed_2_cruise_control_lan
/
Is it possible that a small mass can have a large momentum?
Impulse
• Force applied over a time interval
• Causes a change in momentum
Impulse = Change in momentum
Example problem
• A golfer drives a 0.10 kg ball from a tee giving it an initial
horizontal speed of 40 m/s (about 90 mph). The club and
the ball are in contact for 1 millisecond. What is the
average impact force exerted by the club on the ball
during this time?
Advantage of a long time interval Δt
Safety measures:
Greater impulse:
Rebounding or bouncing
• Two changes in momentum occur.
bouncing ball video momentum change - Yahoo! Video Search.flv
Video clips
http://www.youtube.com/watch?v=S3yZiXw
moJ4
• http://www.youtube.com/watch?v=9iKGfo1
wmOM
Conservation of Momentum
Collisions
In all collisions, the total momentum of the
system remains unchanged.
Elastic Collisions
• Elastic collisions occur when two or more
objects interact and rebound off each
other and continue to travel independently
of one another.
Total Momentum before = Total momentum after
m1i v1i + m2i v2i
=
m1f v1f + m2f v2f
http://www.youtube.com/watch?feature=pla http://teachertube.com/viewVideo.php?vide
o_id=15865&title=Momentum_and_Collisio
yer_embedded&v=JgPSWAp6iK0
ns
Examples
• http://www.physicsclassroom.com/mmedia
/momentum/crete.html
• Notice that each of these vehicles has its own mass and
velocity before the collision and after the collision, but
the total momentum is the same both before and after.
Inelastic Collisions
• Inelastic collisions occur when two or more
objects interact and continue to travel
together as one connected object.
Total Momentum before = Total momentum after
m1i v1i + m2i v2i
=
(m1f + m2f ) vf
Examples
• http://www.physicsclassroom.com/mmedia
/momentum/crete.html
• Notice that each of these vehicles has its own mass and
velocity before the collision, but after the collision, the
masses are added together and they have the same final
velocity because they are connected. The total
momentum is the same both before and after.
Using the equations
1.
Determine if the collision is elastic or in elastic.
2.
Choose the correct equation for the conservation of
momentum.
3.
Insert the known variables from the problem.
4.
Solve for the unknown variable.