Swinger: Can Magnetic Attraction Overcome the Pull of Gravity?

Problem

Can magnetic attraction overcome the pull of gravity?

Materials

• 2 bar magnets
• sewing needle

Procedure

1. Place the first magnet on a wooden table.
2. Hold the second magnet about 2 inches (5 cm) above the magnet laying on the table. Position the two magnets so that opposite poles (north and south) are facing each other.
3. Touch the point of the sewing needle to the bottom of the top magnet
4. Lower the top magnet so that the hanging needle is very close to, but not touching, the magnet laying on the table.
5. Use your finger to push the bottom of the needle to one side, and release the needle as if swinging a pendulum.
6. Observe the movement of the needle.

Results

The needle swings quickly back and forth for a few seconds, and then stops in a straight-up-and-down position between the two magnets.

Why?

Touching the needle to the magnet magnetizes the needle. The needle becomes an extended part of the magnet's pole that it is touching. Because "unlike" magnetic poles (north and south) are attracted to each other, the eye end of the needle is attracted to the opposite pole of the lower magnet. Gravity plus the downward magnetic pull toward the lower magnet do not produce a force strong enough to move the needle away from the magnet it touches. From point A in the diagram, the needle moves toward point B because of both the downward pull of gravity and the attraction toward the lower magnet. The needle passes point B and swings upward to point C, where it is again pulled down by gravity and the attractive magnet pull toward the lower magnet. The height of the swing decreases with each swing, until finally the needle stops and stands still in a vertical position. The strong magnetic pull of the magnet touching the needle keeps the needle from falling, but the lower magnet's pull keeps the needle from swinging freely.

Let's Explore

1. Would standing the needle on the lower magnet affect its swing? Repeat the experiment, placing the point of the needle on the lower magnet. Observe any changes in the speed and time that the needle continues to swing.
2. Would a different-sized needle affect the results? Repeat the original experiment twice, first using a smaller needle, and then using a larger needle. Observe and record any differences in the speed and time that each needle swings.

Show Time!

1. Use the magnets and needle as part of a project display. So that you do not have to hold the magnet, support the upper magnet on a stack of books. As part of an oral presentation, demonstrate the movement of the needle when suspended on the top and bottom magnet. Display diagrams showing the forces acting on the needle during its swing.
2. How does the shape of magnets affect their purpose? Examine different kinds of magnets and their uses. Collect and display different-shaped magnets and/or pictures of magnets, such as magnetic bulletin boards, refrigerator magnets, and magnetized screwdrivers.

Check It Out!

Read about the magnetic fields around magnets of different shapes and discover why a horseshoe magnet can hold up more magnetic material than can a bar magnet of the same magnetic strength. Diagrams showing the magnetic field around each shaped magnet can be part of a report. Enlarged copies of the diagrams can be displayed as part of a project.

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Janice VanCleave's Magnets
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