Growing With Science Blog

Category: Physics (Page 5 of 7)

Weekend Science Fun: Water Sloshing

August 16, 2010 / / 0 Comments

This morning I asked myself a simple question:  “Why, when I’m carrying the cat’s full water bowl up the stairs, does the water slosh over at the top step?”

A question like this can often generate some interesting science.

Gather:

  • a couple of sturdy mixing or soup bowls with sloped sides, at least two different sizes
  • a straight-sided bowl, such as a casserole dish
  • water
  • metronome (optional)
  • water-proof clothing such as a rain jacket (if it is cold out or if the children can’t change clothes if they get wet.)
  • measuring cups (optional)

This is probably best done outside where a little spilled water won’t be a problem. First fill one bowl with water and see what happens when you walk with it held out in front of of you. Does the water begin to move back and forth? What happens when you stop?

Now compare that with a bigger or smaller bowl. Does more water go out over the edge with a big bowl or a small bowl? What about slope sides versus straight sides?

If you have a metronome, try walking at a constant slow pace versus a constant fast pace. See any differences?

You can actually make this more scientific by measuring the amount of water you put into the bowl and how much you have at the end with liquid measuring cups.

What we are seeing is the resonance, or the swing, of the water. When the swing gets big enough, over the edge it goes. This may not seem so important until you realize that the same sorts of forces are acting on the waves and tides of the oceans.

My son suggests I carry the water up the stairs in a straight-sided pitcher. Based on your studies, what do you think of that idea?

waves

The Candy Bomber: A Parachute Challenge for Kids

August 8, 2010 / / 3 Comments

This week our activity is inspired by the middle-grade book Candy Bomber:  The Story of the Berlin Airlift’s “Chocolate Pilot” by Michael O. Tunnell. For a full review of the book, visit Wrapped In Foil.

(Affiliate link)

In Candy Bomber, pilot Gail Halvorsen releases small parachutes over the city of West Berlin after the end of World War II. The parachutes are carrying bundles of candy for the children whose lives have been disrupted by the aftermath of the war. Eventually the candy drops are turned into an official U.S. Air Force operation and more pilots join in. It is a heartwarming tale.

The challenge of building and testing parachutes would be a fun science activity to pair with this book.

A parachute consists of some sort of light material to form the canopy and suspension lines to attach the load.

parachute

Variables to test:

  • parachute materials, such as cloth, plastic bags, paper, etc. Handkerchiefs were used in the Candy Bomber.
  • canopy shape, such as square versus round
  • canopy size
  • length and/or number of suspension lines
  • different shapes and types of candy

Some potential factors to measure:

  • Time of descent (slower is better)
  • Accuracy of parachute flight to a target
  • Safety of load delivery (Does the candy land unharmed?)
  • Distance traveled (if testing outside under windy conditions)

You will need a launch site. We drop ours over the balcony from the second story of our house to the first floor. You might try playground equipment at a park or school that has a stable, raised platform. Keep safety in mind.

Gather:

  • materials to make canopies
  • materials to make suspension lines, such as string or yarn
  • measuring tape
  • stopwatch
  • assorted candy, individual pieces of hard candy with holes in the center would be the easiest.
  • pencil and paper to record results
  • scissors
  • heavy-duty tape to attach suspension lines (optional, but may speed assembly) and to attach load

The simplest parachute to make is a square of material with strings tied to the four corners. Start with lines about 1 foot long. Tie the strings on the corners and bring the strings together at the bottom. Tie on a candy. A single hard candy with a hole in the center might be a good starting point, as long as your children are old enough.

Drop your parachute and measure one of the suggested factors. This is a great project to do with groups.

Here’s a somewhat long video that shows you more details of how to make toy parachutes.

Let us know what you find out about parachutes.

Also, let us know what you think of the book.

Weekend Science Fun: “Cool” Ice Experiments

June 20, 2010 / / 0 Comments

As the temperatures heat up, its time to pull out the ice and do some “cool” science.

1. Ice Spikes

Have you ever seen bumps or spikes come up from the ice cubes in your ice cube tray? SnowCrystals.com has a great discussion of ice spikes, how they form and how to grow some of your own. For more pictures and a movie, try Spikes on Ice Cubes.

2. Ice cube rescues

Give your child(ren) a challenge to “rescue” ice cubes floating in a glass of water with only a piece of string and some salt. Then watch this video to see how it is done.

3. Freezing and thawing water

Freeze water in various-sized containers and then set the ice “sculptures” out to thaw. (Set them in in deep bowl indoors or outside on a sidewalk or patio where a little melt water won’t matter.) Time how long it takes various sizes and shapes to melt with a watch or clock. Does size or shape influence melting time? How?

Try freezing a water-filled water balloon (set in a bowl first). Once it is frozen, what happens when you toss it? What happens when you freeze a balloon filled with air in a bowl of water?

4. Floating and sinking

Create an ice cube boat and float it to emphasize that ice is less dense than water.

Gather:

  • ice cube tray
  • cold water
  • pie plate or shallow bowl
  • plastic wrap
  • toothpicks
  • triangle of paper
  • clay (optional)

ice-boat
Fill the ice cube tray with water. Cover the tray with a tight layer of plastic wrap, which will hold up the toothpicks. Stick a toothpick in the center of each cube, enough so that there is a least one for each child. When the ice cubes are frozen, remove from the tray. Insert a small triangle of colored paper on each toothpick to make a sail, and float the ice cubes in a bowl of cold water (the colder the better). Do the boats float? Do they stay upright? If not, try adding some clay to the bottom until the ice cubes are balanced. (This may be difficult at first, if the oily clay doesn’t stick to the wet ice. I found it did work with patience.)

5. Moving on to dry ice

Dry ice (frozen carbon dioxide) is available at many grocery stores. Just remember that it is much colder than regular ice and will require special handling. Always use gloves, and tongs are a good idea too. Never put dry ice in a swimming pool!

See this Steve Spangler video for some ideas and handling suggestions.

Ice is so much fun to experiment with in the summer. Let me know if you have any other experiments to do with ice or activity tips.

For more information, try these books:

and these related subjects:

Ice Scientist: Careers in the Frozen Antarctic (Wild Science Careers) by Sara L. Latta

Pioneering Frozen Worlds by Sandra Markle

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