### Multiple Choice

### 7.1 Kepler's Laws of Planetary Motion

A planet of mass m circles a sun of mass M. Which distance changes throughout the planet’s orbit?

- $\overline{{f}_{1}{f}_{2}}$
- $\overline{mM}$
- $\overline{M{f}_{2}}$
- $\overline{M{f}_{1}}$

- $12,500\phantom{\rule{thinmathspace}{0ex}}\text{km}$
- $100,000\phantom{\rule{thinmathspace}{0ex}}\text{km}$
- $200,000\phantom{\rule{thinmathspace}{0ex}}\text{km}$
- $400,000\phantom{\rule{thinmathspace}{0ex}}\text{km}$

An artificial satellite orbits the Earth at a distance of 1.45×10^{4} km from Earth’s center. The moon orbits the Earth at a distance of 3.84×10^{5} km once every 27.3 days. How long does it take the satellite to orbit the Earth?

- 0.200 days
- 3.07 days
- 243 days
- 3721 days

Earth is 1.496×10^{8} km from the sun, and Venus is 1.08×10^{8} km from the sun. One day on Venus is 243 Earth days long. What best represents the number of Venusian days in a Venusian year?

- 0.78 days
- 0.92 days
- 1.08 days
- 1.21 days

### 7.2 Newton's Law of Universal Gravitation and Einstein's Theory of General Relativity

What did the Cavendish experiment measure?

- The mass of Earth
- The gravitational constant
- Acceleration due to gravity
- The eccentricity of Earth’s orbit

- $0.810\phantom{\rule{thinmathspace}{0ex}}{\text{m/s}}^{2}$
- $1.23\phantom{\rule{thinmathspace}{0ex}}{\text{m/s}}^{2}$
- $539\phantom{\rule{thinmathspace}{0ex}}{\text{m/s}}^{2}$
- $3735\phantom{\rule{thinmathspace}{0ex}}{\text{m/s}}^{2}$

- It would feel the same if the force of gravity suddenly became weaker. This illustrates Einstein’s postulates that gravity and acceleration are indistinguishable.
- It would feel the same if the force of gravity suddenly became stronger. This illustrates Einstein’s postulates that gravity and acceleration are indistinguishable.
- It would feel the same if the force of gravity suddenly became weaker. This illustrates Einstein’s postulates that gravity and acceleration are distinguishable.
- It would feel the same if the force of gravity suddenly became stronger. This illustrates Einstein’s postulates that gravity and acceleration are distinguishable.