PrepGo

AP Physics C: Mechanics Practice Quiz: Motion of Orbiting Satellites

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 10 questions to check your progress.

Question 1 of 10

A satellite maintains a stable, circular orbit around Earth. Which of the following quantities associated with the satellite-Earth system must remain constant?

All Questions (10)

A satellite maintains a stable, circular orbit around Earth. Which of the following quantities associated with the satellite-Earth system must remain constant?

A) Its kinetic energy, gravitational potential energy, and total mechanical energy.

B) Only its kinetic energy and gravitational potential energy.

C) Only its total mechanical energy.

D) Its kinetic energy, but not its gravitational potential energy or total mechanical energy.

Correct Answer: A

The provided content states that for circular orbits, 'the system’s total mechanical energy, the system’s gravitational potential energy, and the satellite’s angular momentum and kinetic energy are constant.' Therefore, all three listed quantities are constant.

A comet travels in a highly elliptical orbit around a star. Which of the following pairs of quantities are both constant throughout the comet's orbit?

A) Kinetic energy and angular momentum.

B) Gravitational potential energy and total mechanical energy.

C) Total mechanical energy and angular momentum.

D) Kinetic energy and gravitational potential energy.

Correct Answer: C

The provided content specifies that for elliptical orbits, 'the system’s total mechanical energy and the satellite’s angular momentum are constant.' Kinetic energy and gravitational potential energy both change as the comet's distance from the star changes.

A key difference between a satellite in a circular orbit and one in an elliptical orbit is that in the elliptical orbit:

A) The system's total mechanical energy varies, while it is constant in the circular orbit.

B) The satellite's angular momentum varies, while it is constant in the circular orbit.

C) The satellite's kinetic energy varies, while it is constant in the circular orbit.

D) The system's total mechanical energy is not conserved, while it is in the circular orbit.

Correct Answer: C

The content states that in a circular orbit, kinetic energy is constant. However, for an elliptical orbit, the satellite's kinetic energy 'can change.' Total mechanical energy and angular momentum are constant for both types of orbits described.

What is the defining condition for a satellite to achieve escape velocity from a central object?

A) The total mechanical energy of the satellite–central-object system is equal to zero.

B) The total mechanical energy of the system is at its maximum possible value.

C) The kinetic energy of the satellite is zero.

D) The gravitational potential energy of the system is zero.

Correct Answer: A

The content explicitly defines escape velocity as 'the satellite’s velocity such that the mechanical energy of the satellite–central-object system is equal to zero.'

According to the provided text, what is the fundamental interaction responsible for the motion of a satellite orbiting a planet in an isolated two-object system?

A) Magnetic forces

B) Electrostatic forces

C) Gravitational forces

D) Frictional forces

Correct Answer: C

The first point describes the motions of a system 'consisting of two objects or systems interacting only via gravitational forces,' which directly applies to an orbiting satellite.

A satellite is in an elliptical orbit around a planet. As the satellite moves from the point farthest from the planet (apogee) to the point closest to the planet (perigee), how do its kinetic energy (KE) and the system's gravitational potential energy (PE) change?

A) KE increases and PE increases.

B) KE decreases and PE increases.

C) KE increases and PE decreases.

D) KE decreases and PE decreases.

Correct Answer: C

In an elliptical orbit, total mechanical energy (KE + PE) is constant. As the satellite gets closer to the planet (moving from apogee to perigee), its distance decreases, so the system's gravitational potential energy decreases. To keep the total energy constant, the satellite's kinetic energy must increase.

A probe is at a distance *r* from a planet of mass *M*. The escape velocity from this point is given by the equation $v_{esc}=\sqrt{\frac{2GM}{r}}$. If the planet's mass were doubled to *2M* while the distance *r* remains the same, how would the new escape velocity ($v_{new}$) compare to the original ($v_{esc}$)?

A) $v_{new} = 2 v_{esc}$

B) $v_{new} = 4 v_{esc}$

C) $v_{new} = \sqrt{2} v_{esc}$

D) $v_{new} = \frac{1}{2} v_{esc}$

Correct Answer: C

The formula for escape velocity shows that $v_{esc}$ is proportional to the square root of the mass, M. If M is doubled, the new escape velocity will be proportional to $\sqrt{2M}$, which is $\sqrt{2}$ times the original escape velocity.

For a satellite in a perfectly circular orbit, which statement is true regarding its motion?

A) Its velocity vector is constant.

B) Its speed is constant, but its kinetic energy changes.

C) Its distance from the central object and its speed are both constant.

D) Its total mechanical energy fluctuates as it orbits.

Correct Answer: C

The content states that in a circular orbit, both kinetic energy and gravitational potential energy are constant. Constant kinetic energy implies constant speed. Constant gravitational potential energy implies constant distance (radius) from the central object. The velocity vector is not constant because its direction is always changing.

A spacecraft is in a stable elliptical orbit. Which of the following describes the energy of the spacecraft-planet system?

A) The kinetic energy is constant, but the potential energy changes.

B) The potential energy is constant, but the kinetic energy changes.

C) Both kinetic and potential energy are constant.

D) The total mechanical energy is constant, but both kinetic and potential energy change.

Correct Answer: D

According to the provided content, for elliptical orbits, 'the system’s total mechanical energy... is constant, but the system’s gravitational potential energy and the satellite’s kinetic energy can each change.' As the satellite moves closer and farther from the planet, PE and KE are converted back and forth, but their sum remains constant.

An astronaut needs to calculate the escape velocity from Planet Y, which has the same radius as Planet X but four times the mass. How does the escape velocity from the surface of Planet Y ($v_Y$) compare to the escape velocity from the surface of Planet X ($v_X$)?

A) $v_Y = 4 v_X$

B) $v_Y = \frac{1}{2} v_X$

C) $v_Y = \frac{1}{4} v_X$

D) $v_Y = 2 v_X$

Correct Answer: D

The formula for escape velocity is $v_{esc}=\sqrt{\frac{2GM}{r}}$. Escape velocity is directly proportional to the square root of the mass, M. If the mass is multiplied by 4 (while r is constant), the escape velocity will be multiplied by $\sqrt{4}$, which is 2.