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Extend students' understanding by conducting one or more of the following activities.

Follow-up Discussion

All Sciences

Hold a debriefing session in which students share their impressions of the exhibition, their results from their investigations, and the answers they found to the questions they had. Suggest that students use Internet resources to investigate any additional questions. (Refer to the resources section for suggested Web sites.)

Impacts and Cratering

Physical Science

This photo of the asteroid Eros was taken by the NEAR spacecraft.
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Students can create impact craters by varying the velocity or mass of a dropped object, and observing and measuring its effects. Place a large shallow baking pan or box on the floor. Fill with 2 inches of flour. Sprinkle a thin layer of cocoa powder over the surface. Drop a marble straight into the pan near the center. Remove the marble and have students examine the crater that was formed and the material that was ejected. Then drop a golf ball and a Superball in different parts of pan from the same height as the marble. Have students compare the craters that result. Fill over the holes and cover with more cocoa if needed. Have students explore cratering by varying the angle and velocity of the balls. Point out that impact craters are formed by the kinetic energy that is released when a moving mass (ball) hits a stationary body (pan). The formula for determining kinetic energy (K) is half the mass (M) of an object times the velocity (v) squared: K=Mv2. The formula for the velocity of the dropped objects is: v = √2gh, where g is gravity and h is the height from which the object was dropped. For the Earth, gravity is constant at 980cm/sec2. Have students calculate the mass of the balls and the kinetic energy that is released when each is dropped.