Explain why for static electricity to occur between two surfaces that are rubbed against each other, one of the materials has to be an insulator

When the speed of the bottle is 2 m/s, the average maximum height of the beanbag is m.

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Clyde and marilyn are riding a roller coaster. during which section(s) of the track is their potential energy converted to kinetic energy? a. from point b to point c only b. from point b to point d only c. from point a to point b only d. from point a to point b and from point c to point d