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In this lesson, we will learn how to describe the velocities and accelerations of planets, moons, and man-made satellites that are moving along circular orbits.

Q1:

A satellite orbits Earth at an orbital radius of 10 000 km. Its orbital period is 2.8 hours. How fast is the satellite moving? Give your answer in kilometres per second and to 2 significant figures.

Q2:

The Americom-7 satellite was launched on September 14, 2000, and currently orbits Earth at a distance of 35 800 km above the surface. The EOS PM-1 satellite was launched on May 4, 2002, and currently orbits Earth at a distance of 702 km above the surface. Which satellite orbits Earth faster?

Q3:

The diagram shows the orbit of a comet around the Sun. The comet takes 84 years to complete one full orbit.

Calculate the time period of the comet’s orbit in seconds. Use a value of 365 for the number of days in a year. Give your answer in scientific notation to 3 significant figures.

At which point in the comet’s orbit will its speed be greatest?

Q4:

A satellite orbits Earth at an orbital radius of 4 2 2 0 0 km and moves at a speed of 3.1 km/s. The satellite has a circular orbit.

What is the circumference of the orbit of the satellite? Give your answer in kilometers to 3 significant figures.

What is the period of the satellite’s orbit? Give your answer in hours to the nearest hour.

Q5:

A satellite orbits Earth at an orbital radius of 7 720 km and moves at a speed of 7.2 km/s. The satellite has a circular orbit.

What is the circumference of the satellite’s orbit? Give your answer in kilometres to 3 significant figures.

What is the period of the satellite’s orbit? Give your answer in minutes to the nearest minute.

Q6:

A geostationary satellite orbits Earth with a period of hours. Geostationary satellites orbit about 36,000 km above the , moving in the same direction as the Earth’s spin.

Q7:

Mercury travels 364 million kilometers as it makes 1 full orbit around the Sun. Assuming that Mercury has a circular orbit, at what distance away from the Sun does Mercury orbit? Give your answer to 2 significant figures.

Q8:

Titan is the largest moon of Saturn. It has a roughly circular orbit and it orbits Saturn at a distance of 1 220 000 km with a period of 15.9 days. At what speed is Titan moving along its orbit? Give your answer in kilometers per second and to 2 significant figures.

Q9:

The table shows some data about Saturn’s moon, Titan. Using this data, calculate the orbital period of Titan around Saturn. Assume that Titan has a circular orbit. Give your answer in days to the nearest day.

Q10:

Mars orbits the Sun at a distance of about 2 2 8 0 0 0 0 0 0 k m . Assuming that Mars has a circular orbit, what is the distance traveled by the planet as it makes 1 full orbit around the Sun? Give your answer in scientific notation to 2 significant figures.

Q11:

The table shows the orbital periods of three satellites in orbit around Earth. Each satellite follows a circular orbit.

Which satellite is closest to Earth?

Which satellite is farthest away from Earth?

Which satellite is in geostationary orbit?

Q12:

Above what line of latitude or longitude do geostationary satellites orbit?

Q13:

The table shows the heights at which three satellites orbit Earth. Each satellite follows a circular orbit.

Which satellite takes the longest time to orbit Earth?

Which satellite takes the shortest time to orbit Earth?

Eutelsat 113 West A is a geostationary satellite. How long does it take to orbit Earth?

Q14:

The diagram shows two different possible orbits of an object around a star.

Which of the following correctly describes the shape of orbit (a)?

Which of the following correctly describes the shape of orbit (b)?

Q15:

In a solar system, gravity acts between the star and the planets to keep the planets in orbit. Which of the four diagrams correctly shows the direction of the force of gravity acting upon the planet as it moves in a circular orbit?

Q16:

Which of the four diagrams correctly shows the direction of the velocity of a planet, at any one moment in time, as it orbits a star?

Q17:

Planets in a solar system are kept in orbit by the force of gravity acting between the planets and the star. In which direction does the force of gravity between the star and a planet pull the planet?

Q18:

Communication satellites are often placed into geostationary orbits. Why is this?

Q19:

Which of the following is the correct formula for the orbital speed of a satellite following a circular orbit around a planet given its orbital radius and orbital period? 𝑇 represents the orbital period, 𝑣 represents the orbital speed, and 𝑟 represents the orbital radius.

Q20:

Planets that orbit closer to a star move around the star. Planets that orbit farther away from a star move around the star.

Q21:

The diagram shows a planet orbiting a star. The planet has a circular orbit. 𝐹 shows the direction of the gravitational force acting on the planet, and 𝑣 shows the direction of the velocity of the planet.

As the planet orbits the star, the magnitude of the velocity , but the direction of the velocity .

As the planet orbits the star, the magnitude of its acceleration , but the direction of the acceleration .

In which direction is the acceleration of the planet as it orbits the star?

What is the angle between the velocity of the planet and its acceleration?

Q22:

What is the period of the orbit of a geostationary satellite?

Q23:

Earth orbits the Sun at a distance of 1 . 5 0 × 1 0 8 km. Venus orbits the Sun at a distance of 1 . 0 8 × 1 0 8 km. Which planet is moving faster around the Sun?

Q24:

Satellite A orbits Earth in 12 hours. Satellite B orbits Earth in 2 hours. Which satellite is closer to Earth?

Q25:

The diagram shows four planets orbiting a star. All of the planets have circular orbits.

Which planet is moving the fastest?

Which planet is moving the slowest?

Is Planet 3 moving faster than, slower than, or at the same speed as Planet 2?

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