Much Work with Little Effort
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Quick Facts: |
- Grades: K-6
- Two show minimum, or 1 show plus 3 workshops
- 90 minute setup and 60 minute teardown
- 14 foot clearance required over stage (may need to
be in the gym)
- Show runs 55-60 minutes for K-2nd and 70-75
minutes for 3-6th
- Only offered by Dr. Quark
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The all-time favorite science assembly
where kids learn that with physics, they can
do anything! Hoisting 200 pounds (like
their principal) over their heads, lifting
1,000 pounds of classmates, or throwing
the portly Dr. Quark 8 feet high into the air is simply a
matter of understanding Kinetic Energy,
Potential Energy, Friction, and Simple Machines (pulleys,
levers, and screws are demonstrated). Can be
customized for Family Audiences.
Scroll down to look at show requirements,
study guides, and a quicktime video of the assembly.
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Questions
- Can you name 10 sources of Potential Energy? Which are Chemical,
and which are Physical?
- Can you name 10 places where we need to have friction?
- Can you name 10 places where we don't want friction ?
- Can you describe 5 ways to reduce friction?
- What is a simple machine?
- If a simple machine makes you able to move something that you
couldn't without it, what else does it do? (Think of how much rope
you pull in a pulley system.)
- If a simple machine makes it possible for you to do a job faster,
what else does it do? (Think of what goes faster, a bike with a big
wheel or a bike with a small one, and which goes up hill the best.)
- What type of simple machine is each of the following:
- the claw on a hammer
- a shoelace in a sneaker
- stairs
- adjustable feet on a refrigerator
- a peanut butter jar lid
- church key can opener
- nutcracker
- a screwdriver
- Beethoven, the huge St. Bernard, has fallen asleep in front of
the TV, and you want to watch Beakman's World. If you can't wake him
up, how could you move him?
- What are the benefits of levers? What are the limitations?
- What are the values of screws? What are the drawbacks?
- What are the benefits of pulleys? What are their faults?
- There's a see-saw 12 feet long from end to end. If two 50 pound
girls sit four feet from the fulcrum, where should Tony, a 10
lb. boy, sit to balance them?
- If Tony sits 3 feet from the fulcrum, is the see-saw long enough
for Alice, a 50 lb. girl, to balance him? Where should she sit?
- Jack has a 5 foot crowbar. He weighs 50 lbs., and he wants to
move a 200 lb. rock. Where should he put his fulcrum?
- What type of simple machine holds your sneakers closed?
What is the mechanical advantage of your shoelace?
Possible Answers
- Chemical: unlit match, flashlight battery, sugar (for us),
gasoline, dynamite, fire wood, car battery; Physical: water
behind a dam, wound rubber band (like on a toy glider), car lifted on
a jack, a blown-up balloon that isn't tied, snow waiting to slide off
a roof, stretched (or compressed) spring (cocked BB gun)
- GOOD FRICTION: tires on a road (going around a corner and
accelerating or stopping), in the clutch of a car, your feet on a
skateboard, your hands on a field hockey stick, between a tennis
racket and tennis ball, in mountain bike brakes, between a sponge and
a dirty plate, between water and a boat's rudder, between pieces of
wood and the nail holding them, between air and a parachute, between a
matchbook and a match to light it, between a rope and a rappellers
harness, in a window that won't stay up, between the floor and the
wedge holding the door open, in the snaps on your jacket...
- UNWANTED FRICTION: Between a speedboat and water, between ice and
skates, between ropes and pulleys, between a baseball and the air,
between parts of an engine (pistons and cylinders), between a desk
chair and the floor, in the hinges of a door, between a paint can and
its lid, between a bottle and cork, between a sliding door and the
door frame or an old window you're trying to close and it's frame...
- REDUCE FRICTION WITH: Wheels, soap and water, oil (mineral or
vegetable), waxed paper. plastic coating (Teflon),
polishing/sanding/waxing, bearings...
- SIMPLE MACHINES ARE : anything that changes the magnitude or
direction of a force...-or, something that helps us move something
more easily...-or, something that helps us do work faster...-or, A
lever, inclined plane, pulley system, screw, wheel and axle.
- If a simple machine amplifies the force you apply, it also makes
you apply it over a greater distance or for a longer time than without
the machine.
- If a simple machine increases the rate at which work is done, it
requires more force/power for the job.
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- lever
- pulley system
- inclined plane
- screw
- screw
- lever
- two 2nd-class levers connected (therefore considered a complex
machine)
- 1st-class lever to open a paint can, a wheel and axle when turning a screw
- Have fun with this! Point out what simple machines are suggested
and try to get some elaborate complex systems...let their imaginations
go!
- LEVERS: low friction, high efficiency, often gravity assisted,
easy to assemble....BUT very limited range i.e. only a few cm at a
time, often awkward
- SCREWS: huge theoretical mechanical advantage, often
convenient...BUT very limited range, and generally very high friction
- PULLEYS: very flexible, great range with enough rope (imagine
lifting 500 lbs. 10 feet with a 12° lever)...BUT great losses in
efficiency due to friction, requires special equipment
- Tony must be four feet from the fulcrum. This can be demonstrated
with a meter stick suspended by it's balance point and hanging paper
clips from it. Propose some other combinations of numbers and
distances--the kids get into it when they see that it works.
- Alice has to sit 6 feet from the fulcrum. See above suggestion.
- The rock cannot be more than 1 foot from the end: Jack has 40, the
rock has 10, so that's a 4:1 advantage for Jack. However, hopefully
somebody will point out that a 1st-class lever probably isn't the
best option--this is a standard application for a 2nd-class lever if
Jack can lift a small portion of his own body weight (with 6° of bar
beneath the rock, Jack has a 10:1 advantage, and only needs to lift
with 20lbs. to move the rock.
- Answers vary.. A shoelace is a rough pulley system; the
theoretical mechanical advantage is one less than the number of
grommets used..good opportunity to discuss how tight shoes can be (and
sometimes are) tied, but why we don't often make tourniquets of our
shoes (BIG friction across the tongue).
Recommended Reading: The Way Things Work, David Macaulay, Houghton Mifflin Company, Boston, ©1988.
Introduction:
Sometimes a word on good manners for guests is
appropriate, but normally not necessary. This is also an opportunity
for the PTA to let the children know they arranged for this program
(i.e. "This program is sponsored by the PTA. If you wondered where
the money from the wrapping paper went, now you know."). Dr. Quark
will take over after hearing the end of the introduction which is as
follows:
"Today we have a guest Chemist. Let's have a warm ______________
School welcome for Dr. Quinton Quark."
Show Requirements:
- Parking close to the stage door.
- Access to performance space 90 min. prior and 60 min. following performance.
- An outlet somewhere near the stage and an extension cord (20' is long enough).
- 1 black, metal music stand.
- Clean & clear.performance area.
- 14 foot ceiling.
- If show shares the floor with the audience, Dr. Quark will require
floor space 16 feet deep.
Show Volunteers:
- Throughout the show many students will be brought on stage.
Primary criteria are enthusiasm and size; paying
attention also counts.
- During the show I will ask some teacher sitting near the stage to
come forward and hold a kid's hand to steady him/her while
he/she walks along a board. I'll then ask for about a
dozen kids to come on stage. I'll try to get them from the
same class, and I'll also ask their teacher to come on stage to help
supervise them since that teacher will know their names.
- At one point during the program I ask if any of the teachers have
changed a flat tire. If you have, simply raise your hand.
It's important for the kids to see that many people
know how to change a tire, and it makes an awkward moment
when the entire faculty looks as if they couldn't change a tire.
- At the end I need help from any one of the following during a show
with no audience members from 5th grade or older:
- the principal
- the phys ed teacher
- any fit teacher over 150 lbs.
- any 2 teachers with good arm strength wearing comfortable shoes
(preferably sneakers)
Whoever helps for the finale will become a hero! Please note that teacher volunteers will not be embarrassed or asked
to do anything that would make them uncomfortable.
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