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The figures show situation 1 and 2. In situation 1, a positively charged 0.10kg insulating sphere is suspended at rest 0.10m above a large positively charged metal plate. In situation 2, a positively charged 0.20kg insulating sphere is located 0.20m above the positively charged metal plate and is in motion. The magnitudes of the charges on the spheres are the same.

Which of the following best explains why sphere 1 can remain motionless?

The electric field due to sphere 1 and the positively charged plate oppose each other, thus enabling sphere 1 to remain motionless.
The mass of sphere 1 is equal to the force of gravity. However, the mass is opposed by the electric force.
The electric force between sphere 1 and the positively charged plate is equal to the force of gravity between sphere 1 and Earth.
The magnitude of the electric charge on the plate is equal to the magnitude of the electric charge on sphere 1.

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