Unleashing Energy: A Sneak Peek on How Things Work
- Monday, August 18, 2008
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.
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.
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?
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.
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?
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