BuildPhysics

AP Physics 1 · Unit 2, Part 2 · Circular Motion and Gravity

Circular Orbits Practice Problems

Use gravity to explain circular satellite motion. Compare orbit sizes, calculate speeds and periods, and use orbital data to infer a planet’s mass.

12 questions6 conceptual · 6 calculation

Start practice

Free · No account required · Self-paced

Simulation scene from the Circular Orbits lesson.Open interactive practice
A scene from the related lesson. Open the practice to work through the questions.

What you’ll practice

Connect a satellite’s motion with the central attraction

Explain the force and acceleration

Distinguish changing direction from changing speed and predict the path if the gravitational attraction is removed.

Calculate orbital conditions

Find speed, period, center radius, and altitude. Compare satellites at different radii and design a synchronous orbit.

Read an orbital-data relationship

Use a moon’s orbit or a graph relating period squared and radius cubed to infer the central mass.

A question from this set

Why a circular orbit turns

A satellite moves at constant speed in a circular orbit with its engines off. Which statement describes the force and acceleration on it?

  • Gravity supplies an inward net force and inward acceleration, while velocity is tangential.
  • Gravity is balanced by an equal outward force, so acceleration is zero.
  • A forward engine force is needed to maintain the speed.
Try it in the practice set
Why a circular orbit turnsA satellite moves at constant speed in a circular orbit with its engines off. Which statement describes the force and acceleration on it?PlanetSatelliteCircular path · constant speedEngines off
A satellite follows a circular path around a spherical planet with its engines off.

Key ideas

Gravity supplies the required inward net force

A circular orbit needs inward acceleration

The satellite’s velocity is tangent to its path. Gravity turns that velocity even when the speed stays constant and the engines are off.

The orbital radius includes the planet’s radius

A stated altitude is measured above the surface. Use the distance from the planet’s center in the orbit equations.

See the physics

Follow native gravitational motion through a turn

After attempting a question, run the prepared satellite scene. Compare radius or mass variants, track the period, and inspect the orbit-data graphs or rotating-planet comparison.

Use a hint for a starting point or open a worked solution to follow the reasoning. Your progress saves in this browser, so you can return to unfinished questions.

Ready for circular orbits?

Begin with a conceptual question, then work through the calculations.

Start practice