Gravitational potential and comparison with electric fields Quiz
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5 questions, one answer each
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1. What is the gravitational potential at infinity?
- A. Zero
- B. Maximum positive
- C. Infinite
- D. −GM
2. A mass moves away from a planet. What happens to its gravitational potential?
- A. It becomes more negative
- B. It stays the same
- C. It increases (becomes less negative)
- D. It becomes positive
3. The potential at the surface of a planet is −4.0×10⁷ J kg⁻¹. How much work is needed to move a 20 kg mass from the surface to infinity?
- A. 8.0×10⁸ J
- B. 2.0×10⁶ J
- C. −8.0×10⁸ J
- D. 4.0×10⁷ J
4. Which is true of gravitational fields but NOT electric fields?
- A. They are radial around a point source
- B. The force is always attractive
- C. They obey an inverse square law
- D. They have a potential that is zero at infinity
5. Two protons are a distance r apart. If r is trebled, what happens to the ratio of electric force to gravitational force between them?
- A. It falls to one ninth
- B. It rises by a factor of nine
- C. It falls to one third
- D. It stays the same