This lesson includes 15 additional questions for subscribers.

# Lesson Worksheet: Orbital Speed Physics • 9th Grade

In this worksheet, we will practice calculating the orbital speed of an object moving along a circular orbit given its orbital radius and the mass of the object it orbits.

**Q1: **

Titan is the largest moon of Saturn. Assuming that Titan follows a circular orbit, with a radius of
1,220,000 km and an orbital speed of
5.57 km/s, calculate the mass of Saturn. Use a value of
m^{3}⋅kg^{−1}⋅s^{−2}
for the universal gravitational constant. Give your answer in scientific notation to two decimal places.

- A kg
- B kg
- C kg
- D kg
- E kg

**Q6: **

A planet has a circular orbit around a star. It orbits the star at a speed of
17.9 km/s, and the
star has a mass of kg. What is the
radius of the planet’s orbit? Use a value of
m^{3}/kg⋅s^{2} for the universal gravitational
constant and m for the
length of 1 AU.
Give your answer to the nearest astronomical unit.

**Q7: **

Nilesat 201 is a communications satellite that orbits Earth at a radius of 35,800 km. What is the orbital speed of Nilesat 201? Assume that the satellite follows a circular orbit. Use a value of kg
for the mass of Earth and m^{3}/kg⋅s^{2}
for the universal gravitational constant. Give your answer in scientific notation to two decimal places.

- A m/s
- B
- C
- D
- E m/s

**Q8: **

The formula
can be used to calculate the mass,
, of a planet or star given the orbital period,
, and orbital radius,
, of an object that is moving along a circular orbit around it.
A planet is discovered orbiting a distant star with a period of
105 days and a radius of
0.480 AU.
What is the mass of the star? Use a value of
m^{3}/kg⋅s^{2}
for the universal gravitational constant and
m for the length of
1 AU.
Give your answer in scientific notation to two decimal places.

- A kg
- B kg
- C kg
- D kg
- E kg

**Q9: **

Io is one of the four Galilean moons of Jupiter.
Io makes one complete orbit of Jupiter every
1.77 days.
Assuming that Io’s orbit is circular with a radius of
422,000 km,
calculate the mass of Jupiter.
Use a value of
m^{3}/kg⋅s^{2}
for the universal gravitational constant. Give your answer in scientific notation to two decimal places.

- A kg
- B kg
- C kg
- D kg
- E kg

**Q10: **

Phobos is the largest moon of Mars. It orbits Mars at a speed of
2.14 km/s.
Assuming that the moon follows a circular orbit, what is the radius of its orbit?
Use a value of kg for the mass of Mars and a value of m^{3}/kg⋅s^{2} for the universal gravitational constant.
Give your answer to the nearest kilometer.