Art Connections: Seashell Mobiles

1. Get Ready

Spool of string
Assortment of seashells
Assortment of sticks, branches, and twigs between 1 and 3 feet (between 30 and 90 centimeters) in length
Flat board of any length
Masking tape
Hand-operated drill with a bit less than 1/4 inch (about 7 millimeters) in diameter
An adult helper

2. Do and Wonder

Tape the seashells to the board to hold them in place. Then use the hand drill to make a hole in each shell.

Find the longest stick of twig. This will be the top of the mobile.

Take two seashells. Thread a length of string through the hole in each shell. Then attach each string to one end of the twig.

Find the balance point of the twig. Tie a string to it; secure it by tying a knot. Now find the second-longest twig. Thread two more lengths of string through two more seashells, and tie the strings to the ends of the twig. You may also tie some strings at other places on the twig.

Find the balance point of this twig. Attach the string from your first twig to the balance point of the second twig. Secure it by tying a knot.

Find your third-longest twig. Thread several more seashells on strings, and attach them to the twig. Find its balance point, and attach it to the second twig.

Find a place to hang your seashell mobile.

3. Think and Write

Does where you attach the shells to the twig affect the location of the balance point?

Suppose you notice that one of the twigs is hanging at an angle. What can you do to get it to hang straight? Can you get it to hang straight without adding or removing a seashell?

Explanation

The horizontal sticks in a mobile act like simple levers, so you can think of the places the strings are tied as fulcrums. You can change the balance point by changing either the weight of the balanced objects or their distance from the fulcrum of the horizontal stick.

Safety Hints

Have an adult assist you with this activity.

Remember to tape down the seashells before drilling holes in them.

Of course, never hold a seashell as it's being drilled.