### 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 planetâ€™s orbit?

- $\stackrel{\xc2\xaf}{{f}_{1}{f}_{2}}$
- $\stackrel{\xc2\xaf}{mM}$
- $\stackrel{\xc2\xaf}{M{f}_{2}}$
- $\stackrel{\xc2\xaf}{M{f}_{1}}$

- 12,500\,\text{km}
- 100,000\,\text{km}
- 200,000\,\text{km}
- 400,000\,\text{km}

An artificial satellite orbits the Earth at a distance of 1.45Ã—10^{4} km from Earthâ€™s center. The moon orbits the Earth at a distance of 3.84Ã—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 1.496Ã—10^{8} km from the sun, and Venus is 1.08Ã—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 Earthâ€™s orbit

- 0.810 m/s
^{2} - 1.23 m/s
^{2} - 5.39 m/s
^{2} - 37.4 m/s
^{2}

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