# Astronomy

Question 1

If you drop a rock from a tall building on Earth, how fast will it be falling after 3 seconds? Answer in units of meters/second, and only type the number.

10 points
Question 2

When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not?

Copernicus misjudged the distances between the planets.

Copernicus misjudged the speeds at which the planets orbit the Sun.

Copernicus placed the planets in the wrong order going outward from the Sun.

Copernicus placed the Sun at the center but did not realize that the Moon orbits Earth.

Copernicus used perfect circles for the orbits of the planets.
10 points
Question 3

Measurements by astronomers show that, on average, galaxies are moving away from the Milky Way, with the speed of their motion proportional to their distance (farther away, moving away faster). The “Hubble constant” is a number that describes the speed a galaxy is moving away according to it’s distance. The current accepted value of the Hubble Constant (H) is 73.8 km/sec/Mpc. “Mpc” stands for megaparsec, or 1 million parsecs, which on its own is a unit of distance.
The Hubble Constant has some weird units. Which of the following units could you convert the Hubble constant into?

light years

light years / centimeters

seconds-1

1 / parsecs

10 points
Question 4

As long as an object is not gaining or losing mass, a net force on the object will cause a change in:

acceleration

direction

weight

speed

velocity
10 points
Question 5

According to Newton’s Universal law of Gravitation, if you triple the distance between two objects, then the gravitational force between them

increases by a factor of 9

decreases by a factor of 9

decreases by a factor of 3

increases by a factor of 3
10 points
Question 6

“Geosynchronous orbit” is a satellite orbit where the orbital period of the satellite (P) is equal to the rotational period of the Earth (1 day). This allows the satellite to view the same part of the Earth at all times (as it orbits the Earth, the Earth rotates to match).

Suppose we wanted to put a spacecraft in orbit around the sun in a circular “heliosynchronous” orbit, so that the satellite could view the same part of the sun at all times. The rotational period of the sun is 26 days. How far from the sun would a heliosynchronous satellite be? Answer in Astronomical Units with two decimals of precision.

10 points
Question 7

If your mass is 60 kg on Earth, what would your mass be on the Moon?

10 lb

10 kg

50 kg

60 kg

60 lb
10 points
Question 8

The planets never travel in a straight line as they orbit the Sun. According to Newton’s second law of motion, this must mean that:

the planets are always accelerating.

the planets have angular momentum.

the planets will eventually fall into the Sun. 