|
|
This Week's Experiment - #330 Water in a Glass
This week's experiment has its roots in a phone conversation I had with my
friend Mik Jacobs (The Fire Guy, http://members.aol.com/findmik/). He is on a
whirlwind tour, including Hong Kong, California and South Carolina. We were
discussing different ways to explain simple science experiments. Later as I
was doing the dishes, I followed up some of the ideas and wound up with this
one. You will need:
a drinking glass
a sink or bathtub
water
a paper plate or piece of cardboard
We will begin with a common, simple experiment. Fill the glass to the top
with water. Place the paper plate firmly over the top of the glass. Holding
it over the sink (in case it doesn't work), hold the plate firmly in place
and turn the glass upside down. Then release the plate. It should stay in
place, and the water should stay in the glass.
Why? It is tempting to think that the plate is holding the water in, but it
is not. The plate is keeping the air out. The air pressure outside the
glass is holding the water in. How can we show that? Well, first, we can let
some air in to take the place of the water. Keeping the glass over the sink,
pull down on one side of the plate, just enough to let a little air get in.
What happens? The water gushes out. But wait. Doesn't that also fit
with the theory that the plate was holding the water in?
To check that, we need to get rid of the plate. Fill the sink most of the
way with water. Holding the glass sideways, place it in the water. Once it
is totally filled with water, turn it upside down, keeping it under the
surface. Lift it slowly upwards. Though most of the glass is above the
surface,
the water stays inside the glass. As long as the mouth of the glass is under
water, no air can get into the glass, and the water can't come out. The
external air pressure holds the water in, even without the plate. As soon as
the edge of the glass is lifted above the surface, air rushes in, and the water
rushes out.
How can something as light as air hold up that much water? The air around
you is pressing on everything with quite a bit of pressure. At sea level, it
presses with 14.7 pounds on each square inch of surface. If you draw a grid
of one inch squares on a piece of paper, you can place the mouth of the glass
on the paper and see about how many square inches it covers. Multiply that
my 14.7 pounds and you can see that you have quite a bit of pressure pushing
upwards. When the glass is full of air at the same pressure, you have the same
amount of push downwards as upwards. They balance each other. With the
glass full of water, when the water starts to move downwards, there is nothing
to take its place. This produces an area of extremely low pressure. The
higher pressure on the outside is then plenty strong enough to keep the plate in
place.
Have a marvelous week.
These experiments are from Robert Krampf - The Happy Scientist
|
|
|
|
|
Nicholas Academy Index
|
|
Roman numerals, addition, multiplication, order of statehood, state and world capitals, order of presidents, chemical elements, parts of speech, spanish numbers.
|
Explore animation, filmmaking, build online cities, create and share works of art, write stories, create your own web site, read creativity articles.
|
Math games, quizzes, fun websites, printable charts, coloring books, tools. Algebra, geometry, fractions, multiplication.
|
Science games and quizzes, fun science websites, posters, coloring books, experiments, forensics labs and more.
|
Play language arts games, improve your vocabulary, create customized puzzles, make your own book! Download free software in the form of shareware, freeware, and demos.
|
|
Play music games, take free music lessons, explore music theory and history, find great posters.
|
Test your knowledge with these fast, fun, and educational quizzes. Roman numeral addition, world capitals, presidents in order, the elements, world flags, and more.
|
Templates, ideas for personal, educational, children's, business sites, design tips and tools, registration and hosting information, step-by-step instructions, quick and easy web page, web building just for kids.
|
Coloring books, countries of the world, games and quizzes, software downloads, posters, computer jigsaw puzzles, printables.
|
Science can be fun and understandable. Free Experiment of the Week, featuring experiments that are unusual, safe, dramatic, cheap, and fun. From Robert Kramp's Science Education Co.
|
|
Online, via email or through the regular mail. College, accredited high school, free reading and phonics courses, foreign language, history, religion, and more.
|
Arabic, German, Japanese, Spanish, French, Italian, Latin, Russian. Games, free software downloads, free online lessons, newspapers, discussion groups, articles, history, culture, quizzes.
|
Coloring books for kids and adults. Civil war, plants, animals, states, middle ages, cultures, geometric designs, puzzles.
|
Fun and affordable space items for kids, including toys, games, food products, and more.
|
New and used low cost books and textbooks. Websites with open source books and loan programs.
|
|
Artists, wars, armour, castle games, recipes, geography, quizzes, fashions, pictures of weapons, music, old world maps, women of medieval times, medicine, language, and more.
|
Reading systems, loan programs, flashcard, worksheet and test makers, game creators, board games, percentage calculator, puzzle creator, timeline template.
|
SAT, GED, ACT, practice tests, exam preparation. Standardized test practice, content standards listed by state, sample items, scope and sequence, aptitude, essential skills.
|
Parts of speech, civil rights, medieval, periodic table of elements, music, astronomy, world maps with flags, literature, poetry, biology,
|
Books, posters, videos, software, curriculum, courses. Save on teaching supplies, receive free educational materials.
|
|
|
