Gravitational Potential Energy | Physics for Grade 10 PDF Download

The gravitational potential energy (E_p or GPE) of an object (also known as its gravitational store) is defined as:
The energy an object has due to its height in a gravitational field
This means:

• If an object is lifted up it will gain E_p
• If it falls, it will lose E_p

The E_p of an object can be calculated using the equation:
E_p = m × g × h

Where:

• E_p = gravitational potential energy, in Joules (J)
• m = mass, in kilograms (kg)
• g = gravitational field strength in Newtons per kilogram (N/kg)
• h = height in metres (m)

Gravitational Field Strength

• The gravitational field strength (g) on the Earth is approximately 10 N/kg
• The gravitational field strength on the surface of the Moon is less than on the Earth
  • This means it would be easier to lift a mass on the Moon than on the Earth
• The gravitational field strength on the surface of the gas giants (eg. Jupiter and Saturn) is more than on the Earth
  • This means it would be harder to lift a mass on the gas giants than on the Earth

Some values for g on the different objects in the Solar System

Example: A man of mass 70 kg climbs a flight of stairs that is 3 m higher than the floor. Gravitational field strength is approximately 10 N/kg. Calculate the increase in his gravitational potential energy store.

Step 1: List the known quantities
Mass of the man, m = 70 kg

Gravitational field strength, g = 10 N/kg

Height, h = 3 m
Step 2: Write down the equation for gravitational potential energy
E_p = mgh
Step 3: Calculate the gravitational potential energy
E_p = 70 × 10 × 3 = 2100 J