These workshops address each of Newton's laws but particularly reinforce the concept of "Inertia" which is totally new to most students. May also help older kids grasp the concepts of "mass" and "force" and "acceleration".
Given time, we also generate a Distance vs. Time graph (showing the Scientific Method at work) with Zusha, the racing hippo.
Table Cloth Pull: Static Inertia.
Students will get to try
pulling the shower curtain from under various objects on the table and
observe which objects move the least (the ones with the most inertia).
Using the mug, it can be shown experimentally that it has more inertia
when it has water in it...only let the kids do this if it's OK for the
floor to get a little wet. I never let a group have more than one mug
of water, because if they are well-behaved they won't even spill a
drop of that; if they know that's all the water they get, they will
probably be careful with it. Many variations exist; let students be
creative and try their ideas.
Metal Marbles: Particle Spectrometer
This demo shows thereality of inertia in motion. As marbles of various sizes roll past a
magnet, they experience a magnetic force and are accelerated in the
direction of the force (an acceleration is any change, even a change
in direction). Objects with the least inertia (i.e. the least mass)
will undergo the greatest acceleration. This is how different
isotopes of an element are separated, except that atoms are used
instead of marbles, and an incredibly sensitive electromagnet instead
of a chunk of rare-earth magnet. After examining the station and
observing a trial run, students should make hypotheses before rolling
all the marbles themselves. Allow students to complete rolling all
the marbles and making observations before retrieving any from the end
boxes.
Zusha Races: Making a graph.
Motion is a graphic entity,
and while many classes have discussed motion and movement, this will
probably be most classes' first exposure to graphing. This station is
designed to emphasize the importance of "observation" (collecting
data) in science, and to practice the art of drawing conclusions based
on observations (interpreting data). The Hippo will race the length of
the track. The monitor at this station should give a data table and
pencil to each kid, make sure the hippo is ON, and then say "go."
Kids should record (on charts provided) the progression of Zusha at
10-second intervals; these will be announced by the monitor as the
stopwatch passes "10 seconds", "20 seconds", "30 seconds....60
seconds". Then announce "90 seconds" at the proper time (70 and 80
aren't crucial, but it doesn't hurt to announce them also). Kids
should then use the graph paper provided to make graphs of the first
60 seconds of Zusha's travel. Based on these first 6 points, most
kids will observe that their graphs are straight lines. Now ask them
to predict, i.e. hypothesize - FROM WHERE THEY EXPECT THEIR GRAPHS TO
GO - where the dot should be at 90 seconds. Have them compare
results.
Rolling Floor:
Students can demonstrate Newton's Third Law
(Action and Reaction) by walking the length of the floor. It's a
deceptive apparatus. Since experience with running this station is
imperative for keeping it safe, only Dr. Quark can supervise this
station. There are numerous variations for this popular activity.
Some possibilities are: standing two students (of equal size)
back-to-back in the middle and have them walk apart; two same-sized
kids start at opposite ends and walk toward each other, then try with
different sized kids (now we're into unbalanced forces and
acceleration - Newton's Second Law). Once again, the crucial aspect
is getting students to think about what will happen and state their
own hypotheses.
Force Tug 'O War:
NOTE - THIS STATION MAY REQUIRE SOME
PHYSICALITY ON THE PART OF THE PROCTOR. One student (the smallest in
the group) is chosen as the standard unit of force for this activity.
It's nice to introduce the idea of units and standards by posing the
questions "How do we measure time? or length?" and "How was it done
before anyone had a watch, or seconds? Or meters or feet - and why do
you suppose "feet" were chosen?" Now the standard force (we'll call
her Jane) sits on the swing on the scales (if her feet are even
grazing the floor your results will be confusing) and a line is drawn
on each scale to show how much force the student exerts. Now the two
scales graduated to equal forces are attached to each other, and the
kids are divided into even teams (it's good to assign one student the
task of "scale reader"). Before starting the tug'o war, ask the kids
to make a hypothesis about what the scales will read. I usually
attempt to control their efforts by asking, "what will the the Blue
team's scale read if the Red team pulls hard enough to make their
scale read one "Jane" (or whoever is the unit of force)". LAW 3: for
every action there is an equal and opposite reaction. If both teams
pull evenly, both scales will read the same force simultaneously. If
one team pulls harder, that makes an unbalanced force resulting in the
expected acceleration.
If I Had a Hammer:
How to use static inertia to your
advantage IN REAL LIFE! Students will learn how to put the head back
on a hammer handle. People often use mallets to drive the head onto a
hammer by placing the head on the stick and then pounding the head
directly with a mallet. Let kids try this and count how many blows
are required before the head is really tight. Then show them how
carpenters do it: put the head on the stick and gently drop the stick
onto the table top. Inertia will keep the head moving after the
handle has stopped, and force it down onto the handle pretty tightly,
but not nearly tight enough to use. Now hold the handle and invert
the hammer (WATCH YOUR TOES FOR FALLING HAMMER HEADS - I PREFER THAT
HAMMERS ALWAYS STAY OVER THE TABLE!) While still holding the handle
in one hand, use a mallet in the other hand to strike the end of the
handle. Because the head has more inertia (it's more massive) than
the handle, the handle moves through it and gets tighter very quickly
- it may only require one blow this way. To remove the heads, invert
the hammers and gently drop them on the table or floor. Once again,
when the handle stops moving (because the table prevents it) the
inertia of the head will pull it off.
Balloon Canopy:
Have the students discuss which has least
inertia: a helium balloon, an air-filled balloon, or air. Whatever
has the least inertia is the lightest. Then they should make a
hypothesis about what will happen if the wagon with a helium balloon
fastened to the floor and an air balloon suspended from the ceiling is
allowed to accelerate; make them DESCRIBE how it will look. Have a
kid pull quickly on the wagon's handle for a distance of about 10 feet
while the other kids in the group watch from the side. It does no
good to let the kids just run around with the wagon, since once a
constant speed is reached, there is no more acceleration and the
balloons will return to straight position. They can also try giving a
quick shove on the handle. Let every kid try accelerating the
wagon. If the proctor should include, as food for thought, that this
may compare to sitting in your car when Mom stomps on the gas pedal,
it may get the students thinking in terms of their own experience.
However, while this is exactly the same thing, one key factor is the
opposite. In a car, you have more inertia than the surrounding air,
so you accelerate more slowly and feel yourself getting sucked
backwards (like the air-filled balloon). The helium balloon has less
inertia than the air, so it accelerates more quickly and leaps forward
when everything starts up. Because this demonstration is
contra-intuitive, they may not believe their eyes - like the "bobber"
demo done during shows when time permits.
Slapstick Science |
Students and teachers with questions, comments, or suggestions for other things you'd like to see can write Dr. Quark at the above address! He loves mail and will try to answer what he gets!