Download (null): 033.NL1

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10/12/15 & 10/13/15
Resources:
Beach ball demo / levitating can / bearing in
shampoo
Inertia.ppt / Hotwheels track & 3
progressively faster cars
Toppling Tower uDu
Coin & cards demo
Gyroscope/GyroEgg/Motorized Top
Levitron & 500 ml beaker (?) << too hard to
get going
Homework for 10/13:
Bell Work:
10/12: Reprise force definition
10/15: YLDOI:TopplingTower (need blocks)
C. Finish “force balance” as needed
1. Reprise definition of force
2. Teeter Totter w/ 2 BBalls
3. Teeter Totter w/ 3 BBalls
4. Define force balance & “FBD” (remind 2°, do 4 - 8°)
5. Beach Ball: Draw FBD given BB is stationary
6. Conclude: If no motion, then no net force!
7. Levitating can-in-glass: Draw FBD if can is in motion upward
-- even if you don’t know what the forces are!
8. Bearing-in-shampoo: Draw FBD of bearing
a. Seems obvious! Weight > Drag!
b. But is it ??? Let’s
D. NL1
1. History of Science intro (Inertia.ppt): Remember, SDG!
Theories change as new evidence appears!!! (no notes here)
a. Aristotle: No force = no motion
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b. Galileo : No force = no change in motion
c. Hot wheels recreation of Galileo (see 033.NL1.pptx):
1) Less friction = farther travel (demo with Hotwheels
track across marker tray & 3 cars from bad to
excellent)
2) At logical extreme, car would never stop – even though
no force is applied
3) Write NL1 based on observations
4) Reprise bearing-in-shampoo
a) Bearing is moving at constant velocity
b) So, must be no net force
c) So, weight = drag! Net force = 0!
5) YLDOI: Falling Apples
2. Inertia Labette (with embedded notes and demo)
a. Define inertia as stay-puttedness
b. Coin-on-card demo (see p. 347):
1) Each student gets glass, card & 5 pennies
2) Coin is occupant, card is car, finger flick is rear
impact
3) So, what happens when car is rear-ended? (Car moves
forward while occupants inertia tends to keep them in
place – appears to be pushed back into the seat) WHAT
keeps penny in place ??? (Inertia = stay-puttedness)
c. Stack of coins “trick”
1) Stack of 5 or so pennies
2) How can you remove the bottom one without touching the
others?
3) Use card to knock bottom penny out sideways while
inertia of rest of stack keeps them in place
d. What keeps upper pennies in place ???
e. Unfortunate science wordology: Three words that get
confused – inertia, mass & weight
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1) Weight: force exerted by gravity on a mass
2) Mass: quantity of matter and/or measure of inertia but
is not the same as inertia
3) Inertia: tendency to follow NL1 (also called “Law of
Inertia”
3. DO IF NEEDED: “Rear end collision” skit (2 chairs as cars w/
2 Ss, slide student in rear into student in front)
[10]
a. Which direction does front car go?
b. Which direction does driver go?
FINSIH LABETTE
E. Rotational inertia: Again, more clearly shows how “stayputtedness” is NOT the same as mass
1. Gyroscope (and stand):
a. Show that non-spinning g-scope does NOT stay upright
b. Show that spinning g-scope does stay upright
c. Show that spinning g-scope EVEN STAYS HORIZONTAL AGAINST
GRAVITY if it starts out that way! Almost like magic!
2. Gyro Egg
a. charge, start & pass around
b. feel force required to change egg’s orientation – has
stayputtedness due to rotation
c. recap NL1