P6 Science – Gravitational Force vs. Gravitational Potential Energy

Why students are confused between gravitational potential energy and gravitational force?

This is a common area of confusion for Primary 6 students, especially when the topics Forms of Energy and Forces are taught close together.

Both are key components of the Primary 6 Science syllabus, and a clear understanding of these concepts can greatly boost a student’s confidence and exam performance.

In this guide, your child will learn to:

• distinguish between the two concepts, using relatable analogies, structured explanations, and simple activities to reinforce understanding.
• identify what gravitational potential energy means and when it is present.
• understand what gravitational force is and how it acts.
• know how to apply both concepts in real-world examples and exam questions.

Key Differences

How to Explain to Your Child – Use Analogies!

Gravitational Force = Invisible hands of the Earth 

Imagine the Earth has invisible hands pulling everything down. That pull is gravitational force.

• It pulls the apple from the tree.
• It pulls your feet to the ground.
• It pulls a parachute down after it is opened.
• It doesn’t store anything — it just pulls!

Gravitational Potential Energy = Energy stored in an object due to its height

Now imagine you lift a heavy bag onto a high shelf. 

• You have done work against gravity when lifting a heavy bag onto a high shelf, and this work is stored as gravitational potential energy in the bag.
• The higher the object above the ground, the more stored energy it has. This stored energy is called gravitational potential energy (GPE).
• Once it falls, the (gravitational) potential energy is converted into kinetic energy of the falling bag

(Think of GPE as a battery: The object at a height stores energy ready to be converted when the object falls.)

Example:

Rachel released a marble at position A in the rough wooden bowl shown below. The marble rolled to position B and then to position C where it rolled back.

Explanation:

At position A (highest position): The marble possessed the greatest amount of gravitational potential energy as it was at the highest position.

Rolling from A to B: The gravitational potential energy had been converted into kinetic energy, sound and heat energy.

At position B (lowest position): It possessed the least amount of gravitational potential energy as it was at the lowest position but it possessed the greatest amount of kinetic energy.

Rolling from B to C: Kinetic energy had been converted into gravitational potential energy, sound and heat energy.

Common misconceptions to watch out for:

(✔) Correct: It’s always acting on an object with mass, even when the object is not moving.
(X) Wrong: Gravitational force only happens when things fall.

(✔) Correct:  Even light objects have GPE, as long as they’re above ground! 
(X) Wrong: Only heavy things have GPE

Note: Lighter objects (smaller mass) have less GPE than heavier objects.

Question that students can ask themselves when attempting questions:

“Is this about a pull force or about stored energy?”
This simple question helps separate the two ideas clearly.