7.2.1 Understanding Circular Orbital Motion

Question 1

Understanding Circular Orbital Motion

Answer 1

• An object is in orbital motion if the only force acting on it is gravity.
• As the initial velocity of an object launched tangentially from Earth is increased, the orbital path changes from elliptical to circular to hyperbolic.
• The speed of an object in circular orbit is , where M is the mass of the Earth and G is the gravitational constant. The object’s orbital period (T) and its distance to Earth (r) are related according to the formula:

Question 2

In order for a satellite in free fall to maintain uniform circular motion, ______________.

Answer 2

there must be a centripetal force

Question 3

An artificial satellite is to be put into a circular orbit 2.510^6 m above the surface of a planet. The planet’s radius is 6.0510^6 m and its mass is 4.81*10^24 kg. What is the acceleration due to gravity if the satellite makes one circular orbit every 13,700 s?

Answer 3

1.8 m / s^2

Question 4

Which of the following is not correct?

Answer 4

Astronauts riding in an orbiting spaceship are not in orbital motion.

Question 5

Consider a baseball thrown from the top of a tower on the surface of the Earth. You examine four different launches, each with a larger initial velocity as shown in the illustration. Which of the following concerning the orbital path of the baseball is incorrect?

Answer 5

The first launch results in a parabolic path in which the baseball falls to the surface of the Earth.

Question 6

The basic principles or laws are used to describe simple orbital motion. Which of the following is not involved with simple orbital motion?

Answer 6

Newton’s second law of rotational motion

Question 7

The acceleration of a satellite in uniform circular orbit ____________.

Answer 7

• depends on the force of gravity
• depends on its altitude
• is produced by the centripetal force

Question 8

You can determine the velocity of a satellite in uniform circular orbit by applying Newton’s second law, Newton’s law of gravity, and the centripetal acceleration due to gravity. Which of the following is not correct?

Answer 8

The satellite’s speed depends on its mass; the larger the mass, the slower the velocity.

Question 9

True or false?
The force of gravity acting on the satellite orbiting the Earth provides the centripetal force that keeps the satellite in orbit.

Answer 9

true

Question 10

Which of the following is the radial acceleration needed for a weather satellite to be in a uniform circular orbit 300 km above the Earth’s surface? The Earth’s radius is 6.380 km and its mass is 5.98*10^24 kg.

Answer 10

8.94 m / s^2