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

Gravitational Forces Practice Problems

Compare gravitational attraction and field strength, use distances measured from a source’s center, and combine the pulls of several masses.

12 questions6 conceptual · 6 calculation

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Simulation scene from the Gravitational Forces lesson. — A scene from the related lesson. Open the practice to work through the questions.

What you’ll practice

Keep force, field, and center distance distinct

Apply inverse-square comparisons

Predict the effects of changing a source mass, a test mass, or their center-to-center separation.

Convert altitude into center distance

Calculate a planet’s field and its force on an instrument. Infer a source mass from a measured surface field.

Combine sources and compare nearby points

Add gravitational-force components from several masses and compare field strength across a spacecraft.

A question from this set

Moving three times farther away

Two isolated spherical objects attract each other. Their masses stay the same, but their center-to-center separation becomes three times as large. How does the gravitational force change?

It becomes one third as large.
It becomes one ninth as large.
It becomes nine times as large.

Try it in the practice set

The same two spherical masses are shown at center separations r and 3r.

Key ideas

A field belongs to the source and the observation point

Force depends on the test mass; field does not

At one location, replacing the test object changes its gravitational force in proportion to its mass. The source’s field at that point stays the same.

Distance starts at the source’s center

For an exterior point near a spherical world, add the world’s radius to the altitude before applying the inverse-square relationship.

See the physics

Compare physical forces with the measured field

After attempting a question, run the prepared mass or planet scene. Inspect force directions, compare source or distance variants, and use the physical-unit readouts for large or very small systems.

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 gravitational forces?

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

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