Slide 2 Impulse and Momentum Work, Energy, Power, Momentum Slide
3 Egg drop 2 Drop an egg in a beaker Drop an egg in a beaker with a
sponge in the bottom. What do you observe?.
SimilaritiesDifferences________. p47 Slide 4 Impulse 3 Impulse is a
force applied over time To stop such an object, it is necessary to
apply a force against its motion for a given period of timeforce
Impulse = F (t) In terms of impact and impulse, why are airbags in
car a great invention? Slide 5 Impulse 4 Which activity would
require more impulse 1.) Accelerating a soccer ball from rest to
10m/s OR accelerating a medicine ball from rest to 10 m/s? 2.)
Slowing a car from 60mph to 40 mph OR slowing the same car from
40mph to 10mph? 3.) Landing from a jump while flexing the legs
(bending at the knees) OR landing from a jump while keeping the
legs straight (locking knees)? 4.) What can we conclude about
IMPULSE? p47 Slide 6 Bowling ball What happens if 5 I swing a
bowling ball at you? Possibility #1 Possibility #2 Possibility #3
Slide 7 Newtons Cradle What happens if 6 I lift and release one
ball Possibility#1 Possibility #2 Possibility #3 What if I lift and
release more than 1 ball? Slide 8 Newtons Cradle Physics Theres an
app for that! 7 The same principle applies to the suspended-ball
desk toy, which eerily knows how many balls you let go Only way to
simultaneously satisfy energy and momentum conservation Relies on
balls to all have same mass Momentum depends on speed/velocity and
mass Giant Newtons Cradle video Giant Newtons Cradle Slide 9
Discover for yourself. Record in your notebook and on a whiteboard
to share out with the class. 8 Place 5 marbles in the center groove
of a ruler. Launch a sixth marble toward the 5 stationary marbles.
Note and record what happens. Now launch two marbles at four
stationary marbles. Then launch three marbles at three stationary
marbles and so on. Note and record what happens each time. Remove
all but two marbles from the groove. Roll these two marbles at each
other with equal speeds. Note and record what happens. 1.) How did
the approximate speed of the marbles before each collision compare
to after each collision? 2.) What factors determine how the speed
of the marbles changes in a collision? 3.) 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? 4.) What
factors affect an objects momentum? Slide 10 What is
momentum???momentum 9 Discuss with your partner and come up with an
example to share with the class p47 Slide 11 What happens if 10 I
drop one super ball? Slow motion ball bounce I drop two balls
stacked on each other? Basketball and tennis ball p48 Slide 12
Superball Physics 11 During bounce, if force on/from floor is
purely vertical, expect constant horizontal velocity constant
velocity in absence of forces like in picture to upper right BUT,
superballs often behave contrary to intuition back-and-forth motion
boomerang effect Slide 13 Real-World Collisions 12 Is a superball
elastic or inelastic? It bounces, so its not completely inelastic
It doesnt return to original height after bounce, so some energy
must be lost Superball often bounces 80% original height Golf ball
65% Tennis ball 55% Baseball 30% Depends also on surface, which can
absorb some of the balls energy down comforter/mattress or thick
mud would absorb Slide 14 Momentum Momentum can be defined as "mass
in motion." All objects have mass; so if an object is moving, then
it has momentum Momentum depends upon the variables mass and
velocitymassvelocity Momentum = mass * velocity p = m * v where m =
mass and v=velocity Momentum is conserved. Momentum can pass from
one object to another (like the super balls) Slide 15 Momentum is a
vector quantity To fully describe the momentum of a 5-kg bowling
ball moving westward at 2 m/s, you must include information about
both the magnitude and the direction of the bowling ball p = m * v
p = 5 kg * 2 m/s west p = 10 kg * m / s west Slide 16 Check Your
Understanding Determine the momentum of a... 1.) 60-kg halfback
moving eastward at 9 m/s. p = mv = 2.) 1000-kg car moving northward
at 20 m/s. p = mv = Slide 17 Momentum and Impulse Connection To
stop such an object, it is necessary to apply a force against its
motion for a given period of timeforce Impulse = Change in momentum
Impulse = F (t) = m v Slide 18 Check Your Understanding If the
halfback experienced a force of 800 N for 0.9 seconds to the north,
determine the impulse Impulse = F ( t ) = m v Slide 19 Impulse
Question #2 A 0.10 Kg model rockets engine is designed to deliver
an impulse of 6.0 N*s. If the rocket engine burns for 0.75 s, what
is the average force does the engine produce? Impulse = F ( t ) = m
v Slide 20 Impulse Question # 3 A Bullet traveling at 500 m/s is
brought to rest by an impulse of 50 N*s. What is the mass of the
bullet? Impulse = F ( t ) = m v Slide 21 To finish 20 CDP 8-1 CU
(p307) 1-3 PtoGo (p309) 1-2 p49 Slide 22 CDP 8-1 21 Problem #8 Use
the conservation of momentum law to find the speed of Granny and
Ambrose together after collision. Total momentum = 240 kgm/s Total
mass = 120 kg p = mv 240 = 120v v= 2 m/s p48 Slide 23 When is a
collision elastic or inelastic? 22 Phet: Collision Lab
http://phet.colorado.edu/en/simulation/collision-lab
http://phet.colorado.edu/en/simulation/collision-lab Collisions and
conservation of momentum Click on advanced tab for more settings
Green arrows = velocity Yellow arrows = momentum Total momentum
displayed in the chart Finish both sides and get a stamp before you
leave today p49 Slide 24 When is a collision elastic or inelastic?
23 Phet: Collision Lab (finish both sides and get a stamp before
you leave today)Collision Lab Click on advanced tab for more
settings Green arrows = velocity Yellow arrows = momentum Total
momentum displayed in the chart Finish Fridays handout and get it
stamped CU (p315) 1-3 PtoGo (p319) 1-2 p49 p47 Slide 25 PtoGo
(p319) 24 Problem #2 Two 1 kg carts are each moving towards each
other at 2 m/s. They collide and each reverses direction, moving in
the opposite direction at 2 m/s. Draw a diagram showing the carts
before and after the collision. Before the collisionP = mv P =
(1)(2)P = (1)(-2) P = 2 kgm/sP = -2 kgm/s Total p = 2-2 = 0 kgm/s
After the collision P = mv P = (1)(-2)P = (1)(2) P = -2 kgm/sP = 2
kgm/s Total p = 2-2 = 0 kgm/s Slide 26 What did we learn about
collisions and conservation of momentum and impulse from this week?
(at least 5 required) 25 This is our MODEL for MOMENTUM p50 Slide
27 Momentum model- DQ: what can objects do with momentum? 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 4.) Momentum is mass x velocity p=mv 5.)
Momentum can be transferred to other objects when they collide 6.)
Momentum is conserved (none is lost or gained during collisions)
Law of Conservation of Momentum Momentum video Slide 28 Momentum
model- DQ: what can objects do with momentum? 7.) an inelastic
collision is when two objects collide and stick together 8.) an
elastic collision is when two objects collide and then bounce apart
9.) an explosion is a type of elastic collision Math review Review
(song)(song) Review video p51 Slide 29 Elastic and inelastic
Collisions When a Ball hits the ground and sticks, the collision
would be totally inelastic When a Ball hits the ground and bounces
to the same height, the collision is elastic All other collisions
are partially elastic collision Slide 30 Collisions 29 Two types of
collisions Elastic: Energy not dissipated out of kinetic energy
Bouncy Inelastic: Some energy dissipated to other forms Sticky
Perfect elasticity unattainable (perpetual motion) Slide 31 Things
that go bump 30 Record what you see Write a possible explanation on
your whiteboard Slide 32 Collisions and conservation of momentum 31
Number puzzles CU (p329)1-4 p52 Slide 33 Warm-up Questions 32 1.
Twin trouble-makers rig a pair of swings to hang from the same
hooks, facing each other. They get friends to pull them back (the
same distance from the bottom of the swing) and let them go. When
they collide in the center, which way do they swing (as a heap), if
any? What if Fred was pulled higher than George before release? 2.
A 100 kg ogre clobbers a dainty 50 kg figure skater while trying to
learn to ice-skate. If the ogre is moving at 6 m/s before the
collision, at what speed will the tangled pile be sliding
afterwards? 3. Summarize the steps needed to solve question #2. p53
Slide 34 Elastic Collision: Billiard Balls 33 Whack stationary ball
with identical ball moving at velocity v cue 8 To conserve both
energy and momentum, cue ball stops dead, and 8-ball takes off with
v cue Momentum conservation: mv cue = mv cue, after + mv 8-ball
Energy conservation: mv 2 cue = mv 2 cue, after + mv 2 8-ball 8 8
The only way v 0 = v 1 + v 2 and v 2 0 = v 2 1 + v 2 2 is if either
v 1 or v 2 is 0. Since cue ball cant move through 8-ball, cue ball
gets stopped. Slide 35 Inelastic Collision 34 Energy not conserved
(absorbed into other paths) Non-bouncy: hacky sack, velcro ball,
ball of clay Momentum before = m 1 v initial Momentum after = (m 1
+ m 2 )v final = m 1 v initial (because conserved) Energy before =
m 1 v 2 initial Energy after = (m 1 + m 2 )v 2 final + heat energy
Slide 36 Collisions and conservation of momentum 35 Number puzzles
part 2 Slide 37 Momentum Quiz tomorrow 36 You may use your notebook
on all parts of the test Bill Nye Momentum (5 min)Momentum Momentum
is ??? Momentum tutorial Conservation of Linear Momentum (4
min)Linear Momentum How is LM conserved? What is an elastic
collision? Inelastic? Use simbucket.com to prove it! p54 Slide 38
Angular Momentum 37 Another conserved quantity is angular momentum,
relating to rotational inertia: Spinning wheel wants to keep on
spinning, stationary wheel wants to keep still (unless acted upon
by an external rotational force, or torque) Newtons laws for linear
(straight-line) motion have direct analogs in rotational motion
Slide 39 Angular Momentum 38 Angular momentum is proportional to
rotation speed ( ) times rotational inertia (I) Rotational inertia
characterized by (mass) (radius) 2 distribution in object Slide 40
Angular Momentum Conservation Speed up rotation by tucking in Slow
down rotation by stretching out Seen in diving all the time Figure
skaters demonstrate impressively Effect amplified by moving large
masses to vastly different radii 39 Slide 41 Do cats violate
physical law? Cats can quickly flip themselves to land on their
feet If not rotating before, where do they get their angular
momentum? There are ways to accomplish this, by a combination of
contortion and varying rotational inertia 40
