Real Science—Lipper—Spring 2008
How Things Work: A Sneak Peek at
By Aurora Lipper
Every object on Earth is held together by at least one of the
four fundamental forces of nature: the strong force, the weak force, the
electromagnetic force, and gravitation. These four forces are found within all
atoms, and they dictate the interactions between individual particles and the
large-scale behavior of all matter throughout the universe. Since the first two
forces (strong and weak) require the use of a nuclear power plant, we’ll focus
on the other two forces (electromagnetic and gravitation).
Gravitation is the force that is always attractive (never repels
or pushes away). This is the force that pulls matter together and keeps your
feet stuck to the sidewalk. Gravitation causes comets to be slung through our
solar system, binds the moon in its orbit around the Earth, and is the sworn
enemy of major league baseball pitchers everywhere.
The reason you get a shock by scuffing along the carpet can be
explained in the realm of the electromagnetic force. This force determines how
electrically charged particles interact and is either attractive or repulsive. Identical
charges repel each other (two positive or two negative charges).
Electromagnetic force is the source of power used in blenders, dishwashers,
aircraft engines, solar flares, and lasers—and is a culprit in bad hair days
The conservation of energy is the idea that “you get out what you
put in.” When you fuel your vehicle with gas or electricity, that energy is
converted into work you can see (e.g., the car cruising down the road), as well
as things you may not notice (heat from the engine, headlights, sound energy,
recharging your electrical battery, and so on).
We use complicated machines such as a car’s engine to convert
energy from gasoline into work, but there are many simpler ways we can see
energy at work. Machines don’t need to be as complex as the internal combustion
engine—chances are you use several simple machines every day in your home.
Simple machines make our lives easier. They make it easier to
lift, move, and build things. You probably use them more often than you think.
If you have ever screwed in a light bulb, put the lid on a jam jar, put keys on
a keychain, pierced food with a fork, walked up a ramp, or propped open a door,
you’ve made good use of simple machines.
Simple machines use mechanical advantage to do certain things more
easily (or do things that you would not be able to do at all). Mechanical
advantage is like using brains instead of brawn (like using your mind instead
of just muscular strength). With pulleys and levers, you use your “mechanical
advantage” to leverage your strength and lift more than you normally could
handle, but it comes at a price: you trade force for distance. When you use our
pulley system (described later), you can thread it up to lift ten people with
one hand, but here’s the trade-off: you will have to pull 10 feet of rope for
every 1 foot they rise. To figure out the mechanical advantage in a pulley
system, count the number of strings in your system. If there are seven strings,
you can pull with seven times your normal strength.
With levers, it’s a little easier to figure out the advantage,
mostly because there are no strings to count or get tangled up because you are
using fulcrums (picture the pivot point in a see-saw). By moving the fulcrum of
a lever around, you can dramatically change the amount of weight you can lift.
Let’s put these ideas to work and start doing science activities!
Science Activity: Exponential Friction
Find a smooth, cylindrical support column, such as those used to
support open-air roofs for breezeways and outdoor hallways. Wind a length of
rope one time around the column and pull on one end while three siblings or
friends pull on the other end in a tug-of-war fashion. Experiment with the
number of friends and the number of winds around the column.
Science Activity: Simple Tug-of-War Pulley System
Have two people face each other and let each hold a smooth pipe or
strong dowel (at least 18 inches long) horizontally straight out in front of his
chest (you also can use broomstick handles). Tie a length of strong nylon rope
(slippery rope works best to minimize friction) near the end of one dowel.
Drape the rope over the second dowel, loop around the bottom, then back to the
top of the first dowel. Zigzag the rope back and forth between the two dowels
until there are four strings on each dowel. Attach a third person to the free
end of the rope. Thread a 6-inch length of PVC pipe onto the end, and tie the
rope back onto itself to form a handle. The two people holding the dowels will
not be able to resist the pull when you pull on the end of the rope (the end
with the handle)!
Science Activity: Simple Balance
With a 12-inch piece of rope, suspend a flat ruler (from its
center point) from a low tree branch (or stack a big pile of books on a table,
place a ruler between books near the top so part of the ruler sticks out, and
you can suspend the balance from it). When the ruler is in balance, add
identical baskets to each end and place objects in the baskets (or directly on
the ruler). Make one basket slightly heavier than the other and slide it toward
the fulcrum until the ruler is in balance again.
Science Activity: Wedge
A wedge is a double-inclined plane (top and bottom surfaces are
inclined planes). You have lots of wedges at home: forks, knives, and nails,
just to name a few. When you stick a fork in food, it splits the food apart. Make
a simple wedge (think ice cream cone-shaped) from a block of wood and stick the
point under a heavy block (like a tree stump or large book). If you place a kid
on the stump while pushing the wedge, you’ll be able to move them both.
Science Activity: Simple Catapult
Use a spoon and a quarter (placed at the end of the handle). Show
yourself that the longer end of a lever (spoon handle) travels faster and
farther than the shorter end. Think about the position of the fulcrum: What
happens when the fulcrum is not at the center?
Science Activity: Simple Gears
Punch holes in the centers of bottle caps. Flatten out the cap
edges as well as you can (you can place the bottle cap between two boards and then
hammer it) while keeping the circular shape intact. Nail the caps to a small
wooden board so the teeth edges mesh and the gears turn freely.
Science Activity: Belts and Pulleys
Collect a rubber band and a roller skate (not in-line skates, but
the old-fashioned kind with a wheel at each corner). Lock the wheels on one
side together by wrapping the rubber band around one wheel, then the other.
Turn one wheel and watch the other spin. Now crisscross the rubber band belt by
removing one side of the rubber band from a wheel, giving it a half twist, and
replacing it back on the wheel. Now when you turn one wheel, the other should
spin in the opposite direction.
Science Activity: Wheels and Bearings
Stand on a cookie sheet or cutting board that is placed on the
floor (find a smooth floor with no carpet). Ask someone to gently push you
across the floor. Notice how much friction he feels as he tries to push you.
Now place three or four dowels parallel to one another, about 6 inches apart,
between the cutting board and the floor. (Smooth wooden pencils can work in a
pinch, as can the hard cardboard tubes from coat hangers.) Ask someone to push
you. Can you travel easily in every direction, or is your movement restricted
at all? Replace the dowels with marbles. What happens? Why do the marbles make
you go in all directions? In what direction(s) did the dowels roll you?
Science Activity: Ball Bearings
Get two cans (the kind with a deep groove in the rim, such as
paint cans) and stack them. Turn one (still on top of the other) and notice the
resistance (friction) you feel. Now sandwich marbles all along the rim between
the cans. Place a heavy book on top and note how easily it turns around. Oil
the marbles (you can spray them with cooking spray, but it is a bit messy) and the
book turns more easily yet.
Science Activity: Simple Homemade Pulleys
Cut a wire coat hanger at the lower points (at the base of the
triangular shape), and use the hook section to make your pulley. Thread both
straight ends through a thread spool, crossing in the middle, and bend wire
downwards to secure spool in place. Be sure the spool turns freely. Use hook
for easy attachment.
The projects in these photos can be found in the Science Mastery
Program on the Supercharged Science website: www.SuperchargedScience.com.
Aurora Lipper is a real
scientist, mechanical engineer, university instructor, airplane pilot,
astronomer, and homeschool mother of two. She can transform toilet paper tubes
into real rockets and make laser light shows from Tupperware®. Learn how to build catapults, pulley
systems, and more by downloading the Simple Machine Experiments at www.SuperchargedScience.com/energy.htm.
2008 The Old Schoolhouse® Magazine.
article originally appeared in the Spring 2008 issue of The Old Schoolhouse® Magazine. Reprinted with permission from the