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 worldwide.

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.

Copyright 2008 The Old Schoolhouse® Magazine.

This article originally appeared in the Spring 2008 issue of The Old Schoolhouse® Magazine. Reprinted with permission from the publisher.