# What’s the difference between gravitational force and gravitational potential energy?

Attention parents of primary students! Understanding topics like gravitational potential energy and gravitational force is crucial for supporting your child’s learning, especially during Science exams. These concepts are frequently tested, so grasping them well can make a big difference in your child’s performance.

Let’s explore this Science concept together to ensure your child is well-prepared for their exams!

### TLDR version: Gravitational force vs gravitational potential energy

Gravitational potential energy (GPE) depends on the height of the object above ground, while gravitational force (GF) remains unaffected by height.

GPE = mass x gravity x height.

GF= mass x gravity. So gravitational force is always constant, unless we change the object’s mass or change planets!

In P6, the topics of energy and forces are commonly mixed up. This is due to very similar names like “gravitational force” versus “gravitational potential energy”, or even “elastic spring force” versus “elastic potential energy”. So let’s understand the difference between what is energy and what is a force.

Energy is the ability to do work. (Work refers to any life process- yes, even sleeping!)

Energy cannot be created or destroyed, only converted from one form to another. Energy can be stored as potential energy.

When someone says that you have the potential to become something, it means that it’s a possibility for you to become that very thing!

This is exactly how potential energy works. Potential energy can be converted into other forms of energy. (In exams, do not use the word “become”! Use “converted” instead.)

### The 6 types of energy

1) Potential energy

– gravitational potential energy (found in objects at a height above ground)

– elastic potential energy (found in stretched or compressed elastic objects)

– chemical potential energy (found in food, batteries, and fuels)

In PSLE, students can just write “potential energy”. There is no need to specify the three types.

Taken from the 2023 PSLE science syllabus (pg 80)

2) Heat energy

3) Light energy

4) Sound energy

5) Electrical energy

6) Kinetic energy

### Let’s focus on gravitational potential energy (GPE).

GPE is found in objects above ground level.

GPE depends on the height of the object above the ground.

GPE= mass x gravity x height

This means that the higher an object, the more the amount of GPE.

On the summit of Mount Everest, Joe has more GPE than when he was at the base of the mountain.

If a ball is thrown upwards in this trajectory:

What will a graph of the gravitational potential energy look like?

It would look exactly like the trajectory!

However, what would a graph of the gravitational force acting on the ball look like?

The gravitational force does not change! GF is constant.

GF = mass x gravity. Gravitational force is also known as: weight

Gravitational force is a force pulling us to the centre of the Earth. This is what keeps us from flying off into outer space!

GF does not change, unless our mass changes, or the amount of gravity changes (which requires a change in planet!)

Watch this fun video below to see how high you can jump on different planets:

How High You Could Jump on Different Planets in 3D

A force is a push or pull. There are four types of forces.

#### Let’s try this question:

Amie kicks a ball. The diagram below shows the path of the ball after she has kicked it.

The answer is…. 4! Did you get it right?

We can see that high above ground, the girl has GPE.

As she skates down, the GPE is converted to KE.

(If you’re unsure, put in numbers! E.g. 100 units of GPE converts to 90 units of KE + 10 units of Heat energy)

Hopefully this clears up the common misconception between gravitational force and gravitational potential energy!

(Article written by Teacher Yee Ting)

### Test your child’s knowledge here!

We have prepared a Kahoot quiz specially for you to test your child’s knowledge of this crucial Science concept. Try it now [valid till end-March]

https://kahoot.it/challenge/01621827?challenge-id=606853e7-8140-440a-a965-e346dc399f79_1709542514189