# 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 m3⋅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

Q2:

A satellite follows a circular orbit around Earth at a radial distance and with an orbital speed . If the satellite were moved closer to Earth, so that it followed a circular orbit with a radius of , at what speed, in terms of , would it have to move in order to maintain its orbit?

• A
• B
• C
• D
• E

Q3:

A satellite follows a circular orbit around Earth at a radial distance and with an orbital speed . At what radius, in terms of , would the satellite have to orbit in order to have an orbital speed of ?

• A
• B
• C
• D
• E

Q4:

For a satellite to follow a circular orbit around Earth at a radius of 10,000 km, what orbital speed must it have? Use a value of kg for the mass of Earth and m3⋅kg−1⋅s−2 for the value of the universal gravitational constant. Give your answer to the nearest meter per second.

Q5:

Which line on the graph shows the relation between orbital speed and orbital radius for objects moving along circular orbits due to gravity?

• AThe orange line
• BThe green line
• CThe red line
• DThe blue line

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 m3/kg⋅s2 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 m3/kg⋅s2 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 m3/kg⋅s2 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 m3/kg⋅s2 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 m3/kg⋅s2 for the universal gravitational constant. Give your answer to the nearest kilometer.

This lesson includes 15 additional questions for subscribers.